This is the real thing that nails down "RCS" as a totally google thing. Google will forcefully enable RCS for people on carriers that want nothing to do with it. And in that case Google controls the entire process every single step of the way.
Messing with what is supposed to be a carrier standard, as I already think what is happening, puts Google to (in my opinion) a legally unreasonable position in some countries, and I won't be shocked it it will be treated as a carrier with licenses et al. (or rather, lack of licenses, which is just plain bad for Google). I won't be surprised if it turned out that many Googlers already knew that this is a bad idea legal-wise, but the higher-ups have approved this shoehorning.
> I won't be shocked it it will be treated as a carrier with licenses et al.
So, the way it works:
The GSMA isn't some kind of monolithic entity with a great deal of power. Industry players with aligned interests come together, form groups and agree on specs and roadmaps. Technically, RCS should be mandatory with 5G. In practice, it took a great deal of time before a country actually enforced that (China).
Google has seemingly been at the helm of the RCS work group since 2015~2016 with the Jibe acquisition first, then the spec revamp, a.k.a. Universal Profile. RCS was essentially a zombie initiative after ~2012, Google saw an opportunity and filled the void. Telcos aren't stupid, they saw P2P messaging being wiped out by OTT services, and SMS is good enough for A2P. There was little incentive for them.
Now, after a lot of failed experiments, and pivoting from a semblance of federated network to a protocol almost controlled end-to-end, Google got what it wanted: iOS support in North America. The rest of the world is mostly lost to WhatsApp and friends anyway.
Carriers that are on board with Google need to enable the standard registration mechanism used by the iOS client. It shouldn't be a big deal by the way, IMS is central to 4G/5G deployments for VoLTE, VoWiFi, SMSoIP, ... but this changes one important thing from a legal standpoint: now the service isn't provided by Google through an ad-hoc client (Google Messages), but by your carrier.
That said, Google can sell SaaS solutions to carriers. It's up to them to comply with local laws when they decide to provide RCS, regardless of the backend.
I think the EU has bigger fish to fry with the DMA. But Google's tactics might eventually come to someone's attention, as they essentially cornered carriers into adopting Jibe, or giving up on RCS. Somehow the only country that didn't let that happen is South Korea.
Moreover Android could separate the RCS client frontend and backend, like it does for SMS and MMS. But realistically most OEMs don't seem to care, and third party SMS apps are fairly niche.
