I agree 100% i know overrotation is the biggest problem here. Sometimes i meet with me friend ex competition player to relearn some things after my 29 years break from playing and we always end up fighting with this problem
But theres no real effort in getting rotated Maybe It comes from way stronger right leg I stoped tennis at age 14 after multiple fractures in left leg/ankle. One year rehab and still there was a muscle atrophy.
But only solution is more physical prep with this leg
Edit: i wtaching De Minaur playing Michelsen right now. He serve pretty opened still hitting 200 kmh easly. Very fast arm
Edit2 : interesting that hardest server curentlly is doing kinda the same thing: