The argument of security is bunk, Apple are integrating the more widely used RCS protocol into iMessage. It’ll mean they won’t need their own bespoke protocol either. Besides Apple is known for calling stuff security changes when really they rely on obscurity to not notice how insecure components are such as the method iMessage uses to authenticate now.

When done other apps for messaging will explode in commonality and blow the case open. They just need to finish implementing it.

https://www.engadget.com/what-is-rcs-and-how-is-it-different-from-sms-and-imessage-202334057.html