I don't know if it's a bug or a change, but the timing is different in the new version of the 2-12. It looks like once you get the key, locks disappear faster than in the old version.
I don't think locks in other levels are faster, so my question is: is it a change in this level particularly?
On one side, we almost don't have to wait for the hidden key to drop and the end of the level to unlock. On the other, it's sad because you have a chance to be crushed by a saw near the end of the level if you rush
P.S: I don't know if it happens only to me, so if other speedrunners can confirm, that would be great!