While that's true that we use word spomenik for all monuments, I think outside of Balkans it's now recognized as a word describing specific abstract and grandiose type of monument. So world (or Internet community at least) took our word and appropriated it to mean something else.
Anyway, if someone visit one of Balkan countries and ask to see spomenik, expect locals to be confused and would not know what exactly you mean.
More seriously, I think you're exactly right about the adopted internet-English meaning of 'spomenik' and the article is right to make a distinction between this particular (and much more interesting) variety and your more generic strictly-regime-sponsored concrete artblob.
Anyway, if someone visit one of Balkan countries and ask to see spomenik, expect locals to be confused and would not know what exactly you mean.