Does documentation matter if it’s still a closed platform? Imo it doesn’t.
RCS requiring 3rd party servers makes it not a replacement for sms. SMS is a very well thought out protocol that works exactly as intended, it just doesn’t have the bandwidth required for modern media.
Google can call on carriers all they want. It’s still a proprietary google implementation which is no better than Apple. And I trust Apple a hell of a lot more than google (which still isn’t a lot).