I understood from other comments that RCS is the default communication channel in N.America an I can sort of see why you want to give people a somewhat less worse option here than Google's Messenger. But RCS should not be the default imho, because lazy people gonna be lazy. So I hereby endorse you to gently push newcomers towards a safe and privacy friendly default by pre-installing Signal or whatever meets the bar and give it a prominent place.
To me, the only they’re trying to maintain control of is AppleOS-to-AppleOS text communication.
Yes, exactly. Apple and Google are both acting to maintain control and this has resulted in a standard that improves functionality but is effectively poisoned at the technical level. Left to their own devices I'm sure Apple would have preferred to stay with their original solution that is even more closed off.