Did I understand correctly, that the parchment contained 2 alternate instructions for dealing with the room enchanted by Snape ? One side of the parchment contained a comparatively short puzzle, similar to the canon HP, while the other side contained incredibly long and laborious recipe ? When a child or young student is given 2 alternate version of homework, one short and entertaing, while other a boring and laborious pain in the ass, which one do they normally choose ? Voldermort, however, does not believe in simple solutions, he tends to do overkills all the time. Maybe that was the distinguishing feature, which Harry wondered about ?

"... real-world security systems had the goal of distinguishing authorized from unauthorized personnel, which meant issuing challenges that behaved differently around people who were or weren't supposed to be there."