ESA queries on uc migration

Could someone help me with understanding of my son’s ESA award please. We had been asked to migrate to UC and following advice on here it’s gone quite smoothly. Had a statement this week and he will receive the LCWRA as expected. £823. Which is more than he got on ESA.
ESA has now ended.
On discussing with several friends, as they were asked to migrate at the same time, their young adults got about £85 a week more on their esa. Around £244. I’ve googled and am confused.
My son went onto esa income related at age 16. He’s stayed on it. 27 now. Nothing has ever been changed. £161.75 a week. I’m assuming they were put on the new style contributions esa as my son was too young to get that at age 16. Not enough contributions. They are all severely disabled and in the support groups, get same rates of DLA/PIP so why the big range in what they get? Should my son have been swapped into the contributions one at some point and I’ve messed up? I know his ESA has ended but I’m worried I should have done something when he turned a certain age and had the correct contributions or something was incorrectly done. Also if he was potentially entitled to more money on ESA then should his UC be more if it’s protected and is there any comeback to do this? Or am I getting it totally wrong.
Thank you in advance
K