And why should apple (or anyone for that matter) be forced to use googles proprietary code for an “open standard”?

Also,

There is, naturally, a wrinkle here. The RCS standard still doesn’t support end-to-end encryption. Apple, which has offered encrypted messaging for over a decade, is kind of a stickler about security. Apple says it won’t be supporting any proprietary extensions that seek to add encryption on top of RCS and hopes, instead, to work with the GSM Association to add encryption to the standard.

https://www.techradar.com/phones/iphone/breaking-apple-will-support-rcs-in-2024