Google knows this, of course, because all of those messages are now routed through Google. As SMS, they were moving through the carriers, but now they’re going through the carriers and Google.
And since end-to-end encryption in RCS is a proprietary extension, not available to non-Google implementations, all of these new messages are wide open and ready for Google to data mine.
Hooray! Big win for everybody?
I also ANAL, but I did take a contract law class in college and this is a textbook case. If it actually happened. And depending on how the “offer” was worded.