> They may not be able to register with Google, but they can make an RCS app nonetheless.

They can make a "standards compliant" RCS which will be able to connect to literally zero carriers or servers on the planet.

In fact Google Messages "RCS" doesn't even implement the RCS standard. They use a proprietary protobuf api exclusive to Google. Google messages can't connect to any "RCS" servers except Google's.

> Twilio has RCS too

Twilio, Bandwidth etc. are gatekept by Google and are basically just a middleman reselling Google's product.