Reminds me of a story. One bright calm sunshiny morning at freezing with frost on the ground our dog was laying on the front yard, head up and observing the world. My wife said "That dog must be miserable". That dog was not miserable, she was where she wanted to be. She had the option to be inside an attached garage that was almost warm enough for me to be in shirtsleeves. She wanted to be out there. What my wife meant was that my wife would have been miserable out there. Not the same thing.When you say the edge of the nest, are they roosting on the plywood there? (that can't be comfortable)
I know you read where chickens "need" a wide flat place to sleep. I don't believe that for a minute. I've seen mature hens choose to sleep on a 3/4" thick piece of plywood sticking up. They managed fine. I've seen chickens play at perching on a 3/8" thick piece of plywood during the day. They'd often lose their balance after a few minutes, then fly back up there to do it again.
Chickens sometimes choose to sleep on wide flat places. Sometimes they choose to sleep on pretty thin supports.
For those concerned about the thickness I'd say put up a piece of 2x4 for them to perch on instead of the plywood. But for your situation I still think going out there after dark and moving them to where you want them to sleep is your best move.I think so. I did not go out last night to witness the who and how. But it looks like they are roosting on the plywood .