Perhaps they took it out because it's not good level design to intentionally hurt the player in order to proceed.
It is possible to open a cracked floor without falling into it. It requires good timing, though.
You either have to stand on the edge of the cracked tile and move quickly away after about two seconds, or you jump with your Roc's Feather.
But you still have a point there - the designers possibly thought the players didn't expect that this works either. And since it was further complicated by Hardhat Beetles following your path, they were maybe like "alright screw this idea and remove that door, the blade traps are enough."
Yet i don't understand why they didn't simply exchange the cracked tiles for regular holes then...
Also it could be that if somebody had the Roc's Ring equipped, they maybe couldn't figure out why the floors wern't crumbling. I know of other games that give crumbling floor protection, and people often forget to switch it off when they need to sink or fall down or somthing.
Well i'd barely call that a reason

This is merely a ring you use for a short period of time - e.g. in a single room of a dungeon - which afterwards you change back for your prefered ring (with a more universal effect).
If somebody is permanently using the Roc's Ring the player either (a) has no other ring he/she'd like to activate, (b) some severe hole-falling paranoia or (c) simply didn't understand how Magical Rings work :lol: