Yes and no. From what I remember way back in vanilla what would happen is the respawn rate would stay at one level for a bit. After some time of the mobs being killed quickly the rate would increase. It could take a bit though and there was clearly more going on as a trigger than just mobs being killed at a certain rate.
So if someone came in and cleared out an area they might have to do that several times before the increased spawn rate kicked in. I also think there’s a factor for how many people were killing the mobs and it was probably on an area basis, not on which mobs were being killed. An area might be defined differently than you are guessing and if part of it wasn’t getting cleared it might cause the increased spawn not to trigger.
But I certainly remember highly-farmed areas spawning faster after a bit and then slowing down again when people left. I was even trapped a few times by high spawn rates when the other people left and everything respawned too quickly for a few people to handle.