Alright, so. That article. Turf is a kind of moss, is it now. Assume that I have inserted a properly Irish string of obscenities here, and insulted the intelligence of the writer. Turf is partially composed of moss, certainly, but also a number of other bog-growing plants, compressed over a few thousand years in anaerobic conditions into a dense, stringy, soil-like material which burns passably well and for a long time if you dig it up and dry it out. Moss. I ask you. What does he think we are, savages? Turf smoke also smells quite pleasant.

Anyway. To the meat of the question. Short answer: nobody knows. There's just the bog, and in it, butter. No documents, no carved stones, no other evidence. Sometimes the butter is in barrels. Sometimes it's wrapped in cloth or bark. Sometimes it's just a great whacking lump of butter, as in this case. I'm aware of two schools of thinking on this.

The first is plain storage. Because bogs are anaerobic, which means that there's little to no oxygen down in the waterlogged peat, they preserve organic material very well indeed. So it is possible that some long-ago farmer reckoned that she had more butter than she could use, and buried some for later retrieval, much as people in cold climates can put meat out to freeze, and with less risk, probably, of wolves or bears making off with it. For whatever reason, she never dug it up - maybe she forgot she'd buried it, or moved house, or died, or any of a hundred completely unknowable possibilities. The fact that bog butter has been found that dates from the medieval period argues for storage, rather than the more dramatic possible other reason.

... which is ritual sacrifice. We know that other things were sacrificed in bogs, and there are corpses - well-preserved in the aforementioned anaerobic conditions, discovered all the time. They date from about 3200 BCE up to at least the 11th century. Some bear signs of what appear to be ritual sacrifice, and they're often found in area that are the borders between different kingdoms or other land divisions. There are other sacrificial items found in similar circumstances; swords, coins, wooden and metal bowls, and so on, often deliberately broken. But the idea of sacrificing 22 pounds of butter seems odd, even for the Irish.

However. Bog bodies are found pretty much anywhere in the world that there are peat bogs, and it's clear that some of them were accidental deaths, or the concealment of murders, rather than sacrifices. Bog butter is, to the best of my knowledge, only found in Ireland and Western Scotland. You could argue that it's a regional foodway, or you could argue that it's a regional form of sacrifice, and I don't know that there's much to support it one way or other.

Finally, to the recipe for butter being consistent: Yes, absolutely. Butter is very simple. You get cream, you agitate it for a while, and the result is butter and buttermilk. You can add salt to the butter, which helps preserve it. You can drink the buttermilk, if you like sour tastes (I do), or use it in baking if you don't. The agitation could be in a sealed vessel that you shake (which is how the Mongols made butter; in skins that they carried on horseback for a day or two), or in barrel-like churns which have a vertical component that gets plunged up and down in a mildly obscene manner (and there's a riddle in the Anglo-Saxon Riddle Book that makes much of this), or in more modern eras, a small barrel with a few pegs or obstacles inside that gets rolled over and over with a handle. But the basics are the same worldwide; the butter made in 3200 BCE is the same as the butter made now, allowing for a slightly different quality of cream from the breed and diet of the cows.

Sources:

Miranda Jane Aldhouse-Green, Dying for the Gods: Human Sacrifice in Iron Age & Roman Europe (2001)

Caroline Earwood, 'Bog Butter: A Two Thousand Year History' in The Journal of Irish Archaeology, Vol. 8 (1997), pp. 25-42