It really does not take much effort to Google.Were that the case, it wouldn't say that Apple was adopting UP. It would say Apple was adopting Jibe. But it's not because they're not the same thing. Jibe is Google's build of RCS, it's not UP. According to jibe dot google dot com Jibe is a platform that supports UP. Therefore it is not UP itself. Jibe also is only supporting Android currently per the GSMA's site.
By aligning on a universal RCS profile, mobile operators will be able to deploy a consistent RCS implementation, feature set, and configuration. The Android RCS client provided by Google will be based on the universal profile, enabling consumers to access RCS services on their devices. Features such as group chat, high-res photo sharing, read receipts, and more, will now become part of the operator messaging experience, enhancing the experience of over 4 billion SMS users worldwide1. GSMA RCS advanced calling features will also be supported in the future by Google.

Global Operators, Google and the GSMA Align Behind Adoption of Rich Communications Services
Operators align on universal RCS profile; Google to provide RCS messaging client in Android Barcelona: Global operators, including América Móvil, Bharti Airtel Ltd, Deutsche Telekom, Etisalat, Globe Telecom, KPN, Millicom, MTN, Orange, PLAY, Smart Communications, Sprint, Telenor Group...



RCS Business Messaging | Google for Developers
Bring branded, interactive mobile experiences to the default messaging app with Rich Communication Services (RCS).

Nobody expects every device to migrate. That is an unrealistic expectation. The problem is SMS/MMS are old protocols that need to be replaced and RCS is there to replace it while keeping SMS/MMS as fallback as they are not data intensive. Its the same reason why 2G and 3G cell networks still exist even though most modern phones use 4G and 5G is the default and fall back to 2G/3G when 4G and 5G is not available."People are migrating" until all are done migrating (which won't be done by the time Apple implements RCS), problem exists, and won't be solved "entirely" (using your word) until then. What's your point?
" were starting to default to Google and Google has made so anyone can use RCS" - Google doesn't exist in China. Google isn't the end game for 100% RCS. China slowly rolled RCS implementation a few years ago among the big carriers.
It is very relevant because Apple uses it as fallback for when iMessage fails. Its not going away, it will stay as fallback.Don't see the relevancy in your iMessage falling back to SMS.