My guess is that a secret was placed there but the room was different, and playtested this way, then it was modified to add an elevator, but not playtested for

My guess is that a secret was placed there but the room was different, and playtested this way, then it was modified to add an elevator, but not playtested for the secret then, and the thing slipped through and sticked. Or that for some reason at a given point during playtesting the engine had a bug that would allow the secret to be triggered, and a later global fix for that situation made the secret impossible to trigger.