Yes, no, possibly.

There are no other accounts I can find of sacrifices to Wotan during World War I, the closest I can find is a heavily biased rewriting of the practice of nailing money and cheques for war bonds onto the wooden statues of Paul von Hindenburg, Chief of the General Staff.

This 1936 account, by English writer John Wheeler-Benjamin, entitled The Wooden Titan is clearly written under the shadow of renewed German militarism:

These statues […] were huge, crude and rugged, and recalled the primitive sculptures of an earlier civilisation. They were indeed a ‘throw-back’ to the images of Thor and Odin, the Nordic war-gods so dear to an earlier German tradition, and to them were made sacrifices in a truly Nordic spirit, sacrifices not of garlands or of doves but of iron nails hammer into the figure till they stood out ‘like quills upon the fretful porcupine.’

Other phrases include “underlying streak of paganism in the German character” and “a fierce pagan sadism”, which is rather a lot of meaning to take away from people nailing cheques to a block of wood.

It's not obviously relevant (although it's a fun read), but the wild rhetoric actually casts more light on Jung's claim than anything short of turning up a newspaper report of animal sacrifice and rune casting in a Bavarian newspaper. Indeed, it's clear from his writing that when Jung talks of Wotan, he is in fact talking about an archetype - one of energetic 'blood & soil' nationalism, described here in his 1936 essay Wotan, Neue Schweizer Rundschau:

What is more than curious – indeed, piquant to a degree – is that an ancient God of storm and frenzy, the long quiescent Wotan, should awake, like an extinct volcano, to new activity, in a civilized country that had long been supposed to have outgrown the Middle Ages. We have seen him come to life in the German Youth Movement...

Armed with rucksack and lute, blond youths, and sometimes girls as well, were to be seen as restless wanderers on every road from North Cape to Sicily, faithful votaries of the roving god. Later, towards the end of the Weimar Republic, the wandering role was taken over by thousands of unemployed, who were to be met with everywhere on their aimless journeys. By 1933 they wandered no longer, but marched in their hundreds of thousands. The Hitler movement literally brought the whole of Germany to its feet, from five-year-olds to veterans, and produced a spectacle of a nation migrating from one place to another. Wotan the wanderer was on the move.

By way of a quick round-up of Jung's lukewarm attitude to National Socialism through the archetype of Wotan, Michael Gellert writes in The Eruption of the Shadow in Nazi Germany that:

Jung also recognized the positive aspect of this god, for he appeared to reanimate the depressed spirit of Germans. This account for Jung’s initial hopes, in the very early day of the Nazi movement, that it might turn into something positive – a view he quickly abandoned when he saw the negative effects this god was having upon German society.

Jung gave his original Psychology and Religion lecture in 1938, at which time his enthusiasm for the spirit of Wotan infusing the Germanic world was beginning to wane. Speaking to Knickerbocker magazine in 1939 he described Hitler as a medicine man and demagogue, seeing in eyes the "expression of a seer" and explaining that he was "the loudspeaker which [amplifies] the unheard murmuring of the German soul" and "like a man who listens attentively to the stream of inspiration delivered in a whisper from a hidden spring."

We must take Jung's claims of sacrifice in the trenches alongside his dissatisfaction with the ideological sound and fury. His Psychology and Religion lecture emptied both barrels against mass movements and his statements about Wotan being reborn in the aftermath of the Great War suddenly make a lot more sense if you replace Wotan with "National Socialism":

Everybody was astonished at the pagan tendencies of modern Germany… thousands and millions of Germans yet unborn in whose unconscious the Teutonic cousin of Dionysus – Wotan – came to birth during the Great War. In the dreams of the Germans whom I treated then I could clearly see the Wotanistic revolution coming on.

The "Wotanistic revolution" is now a foreboding thing indeed, and he's seen its like before - in the slaughter of the Great War. In 1940, Jung's books were banned in Nazi Germany and burnt in France.

The good news is that even if we accept that Jung was talking figuratively of sacrifice to Wotan (or conjuring up a convenient fiction as a rhetorical device - he wasn't a historian or documentarian, after all), there remains the possibility that such a thing did actually take place.

There was certainly a renewed interest in Norse mythology in the run up to World War I. This is most obviously represented by the blockbuster opera series that was Richard Wagner’s Der Ring des Nibelungen.

However this also manifested in worship and in 1902 Austrian mystic Guido von List who began to embellish their eclectic mixture of Hinduism, Buddhism, Eastern spirituality and racism with worship of Wotan, the Germanic form of Odin, and rune magic, which involves inscribing 1st Century Scandinavian/Germanic runes to produce desired effects.

List believed - courtesy of Friedrich Fischbach’s Die Buchstaben Gutenbergs (1900) - that believed that a secret Aryan priesthood had developed this knowledge, and - alongside Jorg Lanz von Liebenfels - formed the Guido-von-List Gesellschaft (Guido von List Society) and the Armanen Orden to further his political aims of German-Austrian unification, virulent anti-semitism and the practice of a new system of rune magic inspired by the ‘Rune Song’ in 13th Century Norse poem Hávamál.

Lanz’s contributions to nationalist occultism were similarly great, resurrecting the Knights Templar as the Ordo Novi Templi (Order of the New Templars) which believed in a struggle between chivalrous Aryan supermen and non-Aryan beasts. Popular in Vienna, ONT brochures are believed to have had a significant impact on a young Adolf Hitler, but that’s us getting ahead of ourselves.

Völkisch occultism - include the worship of Wotan - was a presence in the run up to World War I, flowering again in the 1920s and - most dangerously - the 1930s. Without doubt his followers were active throughout the war and there were 75 Völkisch groups in Germany by 1918 (Hitler enthused in Mein Kampf that "the basic ideas of the National Socialist movement are völkisch and the völkisch ideas are National Socialist.")

Hitler - as if you hadn't seen more than enough of him in this post - returns to place Wotan firmly in the trenches and in 1915 he put pen to paper and wrote a poem praising the Norse god:

I often go on bitter nights/ To Woden's oak in the quiet glade/With dark powers to weave a union/The moonlight showing me the runic spell

I know it's perhaps not as conclusive as you hoped, but to wrap up: Jung may not have been describing a real event or the literal worship of Wotan, but worship of Wotan was present. It's a coincidence in the sense that it may not have been what Jung had in mind, but not a coincidence in the slightest in that it was born out of the same ideological and cultural root.

Sources: Futhark: A Handbook of Rune Magic by Edred Thorsson, Black Sun: Aryan Cults, Esoteric Nazism, and the Politics of Identity by Nicholas Goodrick-Clarke, C. G. Jung's Psychology of Religion and Synchronicity by Robert Aziz, From the Life and Work of C.G. Jung by Aniela Jaffé, Unholy Alliance: A History of Nazi Involvement with the Occult by Peter Levenda, and Nazi Germany: Exploring the Theory of Archetypes by Nicholas Adam Lewin