This doesn't seem correct. RCS is supposed to be supported by you mobile provider, if it isn't only then your messaging app on Android will use Google's service. The whole protocol was meant to be open to entice companies to adopt it.
I understand Google dropped don't be evil, but they are not a villain in every story.
What a weird evil slow burn Google is doing. AOSP used to be an entire open phone operating system for the most part, (aside from binary driver blobs and some DRM stuff) but with each passing year, they close-source everything. It used to be a big proud point Android users celebrated, "oh well I can go read my source code, unlike iOS!" Annnnd....nope.
I want a new mobile OS to replace the shit sandwich of Gappleoogle.