Fuck off Google. This makes me think that RCS is a steaming pile that is easily susceptible to hijinx unless Google blocks power users from their hardware.
It boils down to the same thing it always does, greed. They want control of the protocol, and they want all of the messages flowing through their app, and their servers, so they can track who you're talking to, and possibly extract advertising and profiling keywords from your messages. Idk if they're actually doing that last thing, but it wouldn't surprise me. They scan literally everything else.