Google made a e2ee extension on top the standard that deviates from the RCS spec thus it might as well be considered another spec all-together as it’s no longer able to communicate with adopters of the plain RCS protocol in a meaningful way.
Their extension is proprietary and unavailable to anyone except themselves and Samsung. This means that Google is making a bad faith argument as they’re not advocating for RCS, but their own incompatible version of it.
RCS is extensible and allows for capability discovery. Adding an E2EE extension doesn't really "deviate" from the spec but rather builds on top of it. Google's client can still communicate with other Universal Profile clients; the messages just aren't end-to-end encrypted.
And Google has said that they plan to switch to MLS [1]. Releasing their own E2EE spec more widely at this point would be pointless.
On top of that they’re acting like spoiled children used to getting their way, pointing fingers, because they ‘lost’ the instant messaging war.