The NYT article suggests that one person validated the list—however that one person is an avid word game player, and is in fact the developer’s partner, for whom the game was created—so said validator likely had a deep vocabulary of highly arcane words!

Also, how many words are not on the list? I tried “Punic” today (granted that might be considered obscure as well) and it wasn’t accepted. I just checked “Dutch” and it is okay while “Irish” is not.

Apparently there are two word lists: one for the word to be guessed and one to validate user guesses. I imagine vozhd and waqf would appear in the latter lit but not in the former.