If Apple enabled RCS in messages back then, but the recipient was not using RCS, then Google now has the decrypted text message, even when RCS advertises itself as E2EE. With iMessage, at least I know all of my messages are E2EE when I see a blue bubble.
Even now, RCS is available on Android if using Google Messages. Yes, it's pre-installed on all phones, but OEMs aren't required to use it as the default. It opens up more privacy concerns because now I don't know if my messages are secure. At least with the green bubbles, I can assume that anything I send is not encrypted. With RCS, I can't be certain unless I verify the messaging app the recipient is using and hope they don't replace it with something else that doesn't support RCS.
Having iMessage available to everyone regardless of their mobile OS.
Their words or your words?
By what? It's impossible for a process to know for sure if the system is rooted or not. A rooted system can present itself to a process to look like a non-rooted system if it's engineered well enough.
I'd bet that most of these apps probably just check if "su" returns a shell, in which case perhaps all that's needed is to modify the "su" executable to require "su --magic-phrase foobar" before it drops into a root shell, and returns "bash: su: not found" or whatever if called with no arguments.
That was true 20 years ago, but most smartphones these days have cryptograhically-verified boot chains and remote attestation of how the boot went.