Encryption was never part of the RCS standard, and Google has been gatekeeping the encryption solution that they’ve been using… which is why there aren’t a lot of E2EE RCS clients floating around.
Google finally conceded several months ago, and now encryption will be part of RCS and managed by an independent working group that Google, Apple, and others can contribute to.
Phase 1 of RCS is about implementing the unencrypted foundation of the protocol. Encryption is supposed to come when the working group has aligned.