the creator throwpup removed them as they didn't fit the vision of the game she wanted. it was mentioned a couple times in the discord so i'm paraphrasing. having stamps sort of incentivizes people to search for content and treat it as a number, like a collectable. throwpup wants the secrets and special scenes to be truly secret- meaning if you find it, it feels like something maybe not many other people have seen. furthermore people would often try to get all the stamps after finishing the game, which meant it sort of "game-ified" scenes or content, instead of naturally stumbling upon it- which is what she wants.