The reality is that Google doesn't support RCS, it supports Google Messaging which is built on RCS. Apple is supporting the GSMA standard RCS. It was noted that RCS isn't new, it has been around since 2008. It is also noted that it is not supported by a number of carriers to this day. It is not a ubiquitous standard. It is incumbent on Google to drop the enhancements that make their product incompatible with the standard, or work with the standards body to have their enhancements incorporated into the standard, for free use. One of those enhancements is message encryption. That's why the bubbles are still green in RCS on iOS. To indicate to the user they are not communicating over a secure channel.