It could be just another way to monetise in-game indeed, but it could work only if a unique item (skin, weapon, armour) cannot be reproduced and if only one player got that item. There could be several, but it would have to truly be unique, one and only, for it to fit with the NFT brand. Otherwise, if it can be reproduced or if there are several of that kind, it's not different than bonus content or rare items that anyone can have.