I cannot find my source unfortunately poked around a bit. Unfortunately this article was better than even the ones I was finding.

Google apple agreed to increase android security for the deployment of RCS to both platforms. This directly looked like enforcing root detection and safety net(now play integrity) enforcement to use RCS. I’m speculating restricting side loading is also part of that agreement. It would make sense considering it’s forbidden on apple.

Really starting to wonder what they signed with apple to get RCS. Seems to be they sold the soul of android.