The seats are assigned. People have been standing in line for 15 minutes now. Why on earth would anyone want to stand there, when they could just sit and wait until the line clears?
I understand wanting to get off a plane ASAP, but boarding? You just end up sitting on the plane, waiting for everyone else to get on.
Coats take space in the overhead whether they’re in a bag or not.
If you don’t need your coat to board the plane then you’re lucky.
None of the airlines have a rule about coats in the overhead so you’re fighting on a hill that doesn’t even exist.