How am I supposed to earn them if I don't even know what they expect me to do for them? Why do these exist? I haven't even encountered a game (not even a Fromsoft game, and those guys are notorious for being vague and not forthcoming with info even for guide books) where the hidden achievements were not already listed by a 3rd party somewhere outside of the game day 1, so why not just show them in the damn game?
There's a difference between knowing there is a puzzle to be completed and being given the solution to the puzzle. Achievements should direct you to the fact there is a puzzle; they don't need to give the solution to the puzzle.