instead of pushing the flimsy door:
move player to Hidden Space, without printing a room description.
This is basically a bespoke phrase for exactly this case. (I think “silently” only works for some kinds of actions, “silently try opening the flimsy door” or something like that.) Basically, the I6 code for moving things calls a special routine when the player is the thing being moved, and it performs a looking action (or an I6-level looking action) unless it’s called with the “without printing a room description” flag.
I’m not quite sure why
instead of going south in Vomitorium:
move player to Street.
would print two descriptions though. It seems like the “instead” should preempt the move to Street, and then the “move player to Street” would move the player to the Street and print a room description. If I try it with a Carry Out rule it does print twice, though.