Wait... you're saying that Apple didn't want to do something proprietary? Seriously? Apple's famous for that. It's the foundation of their walled garden.
And I welcome their participation in making the standard better. But the point is that they have ignored the standard (and standards in general) for many years. The only reason Google implemented encryption in their RCS app is because they got tired of GSMA and the carriers dragging their feet and bickering, so they went around them. If Apple hadn't ignored RCS and had instead actually engaged with GSMA 5 years ago, we'd probably already have E2EE built into the protocol. There's no way GSMA or the carriers could have ignored encryption if both Google and Apple had been involved.
As it stands, I sincerely hope that Apple's weight forces the issue of E2EE in the RCS protocol. But I also sincerely doubt that they're all that serious about it, for two reasons. First, if they were serious, they would have engaged years ago to make it happen. Second, encryption only serves to make iMessage less attractive.
But I am willing to be proved wrong. If Apple actually makes encryption part of the RCS standard, I'd be thrilled.