There's really no reason to claim its non-functional; its just not useful for games against arbitrary players.
But its hardly a complex adaptation, requiring but a few games to achieve proficiency (this I know from my own experience with an ornamental set, against my brother)
Anyone you play with repeatedly can be played with on a variant set; and since I imagine most don't only play against randoms in a park/tournament, there's quite a bit of use to find.
And as the article notes, knowing an additional set doesnt detract from knowledge of the first (bilingual)
Tbh, the only reason I can think of to explicitly deny owning or using non-standard set, ignoring random pick-up games and tournaments, is either pretentiousness or genuine love for the Staunton set