Maybe theres a sensory issue that he is dealing with... maybe the feel of the diaper bothers him or the actual act of laying down throws off his proprioception and that makes diaper changes traumatic? Have you tried other brands of diapers? Or even cloth diapers. Maybe work on some proprioceptive exercizes as well. My little one did the same thing when he was little and we were able to work through it by ruling out issues one by one.

Might want potty training, uncomfortable to lie down to be changed anymore. Potty training, get a bunch of prizes from the dollar store for him and give him one each time he sits on toilet and stays. You will need potty seat. My kid was afraid of the toilet, so we had to do social stories around the sewage system to reassure him where the poop went and that the toilet would not swallow him. Captain underpants movie also got him highly interested in the toilet. We tried several potty seats and none except this one was comfortable for him- https://www.babybjorn.com/bathroom/toilet-train...

Is it possible he is ready for potty training? If he hates the diaper, it seems like a good incentive. I also agree that you might try cloth diapers. They are not as much work as people think they are.

I agree it's probably sensory due to the fabric of the diaper. I hope you find a solution to make diaper change easier.

Sensory issues- probably does not like being without a diaper? Someone suggested using a towel between changes long time back. Maybe give that a try. Hope it helps.