I think the phrasing is important here.
Later next year, we will be adding support for RCS Universal Profile, the standard as currently published by the GSM Association.
If Google’s & Samsungs implementations aren't compliant with the GSM associations’ standard then I don’t think this is going to work how people are expecting it to. The stuff Google has added to RCS messaging has all been their own implementation of it and not part of the standard, and as far as I’m aware android RCS gets routed through Google’s servers.
I wonder if RCS support is Apple trying to appease the EU with the DMA stuff forcing messaging apps to be interoperable with each other.