Doesn't really help the argument that it is a proprietary Google technology. The fact that it had to be "made available" to Apple means that it isn't an open standard and requires trusting Google, which many of us don't.

Citation?

Beeper was explicitly told it was not available to others when they wanted to implement Google's encrypted RCS on their Android client.

https://twitter.com/ericmigi/status/1557050351974420480

Encrypted RCS should be a standard. When it is Google should adopt the standard, not its proprietary version. In the meantime I want Apple to implement standards, not proprietary Google technologies.

Under what terms, and with what promises?

If Google's strategy was anything other than "get Apple to adopt, then screw them", Google would have contributed the enhancements back to the standard.