It seems like most are doing that but some are dropping rapidly, although not in a freefall.
The first few look precipitous but you don't see them approach the ground, later in the video you see one that's coming down very fast and then makes a reasonable effort to brake when it gets near the ground.
Edit: Most of them are doing a fast controlled descent, a few seem to have just powered off and become rocks.
There's no collective so you can't "flare" for landing like a helicopter, but during autorotation the terminal velocity is still much lower than if the blades were fixed.
The drones in this video fall a lot slower though. This looks like controlled descent, not autorotation.
it's not that straightforward, whether or not braking or freewheeling causes more drag depends on the prop.
[1] https://www.rcgroups.com/forums/showthread.php?3753127-Freew...