I understand Portugal joined the Allies during the war, so how could Spain not have had any contribution that is worth mentioning in the second, otherwise quite detailed and enlightening historical overview the Great War?
It's not even noted that they stayed neutral; I find it hard to believe that a country bordering on 2 belligerents, and probably affected by the blockade and the total submarine warfare just as much as Germany and Britain would not merit at least a few lines in passing.
I don't understand your question. Spain was a neutral country during WW1 and as such it didn't have a huge effect on the war apart from being a supplier of ironworks, foodstuff, textiles and coal for the belligerent countries, as well as chemicals and light weapons, mostly for the allies but also some to the central powers. But still Spanish industry was not very developed and spread, and as such the industry from the USA had a far far greater effect on the war than the Spanish one.
Is your question about what effect did Spain have on the war? Or about the ignorance of Spain on WW1 historiography?