Comment by jazzyjackson

Yes but there are different specs that “compatible” apps will have to adhere to, basically until everyone is always running auto updating software to the latest version supporting RCS 4.0

Long story short somebody preferred to “ship it” instead of waiting to figure out how to make encryption compatible between iOS and Android. I guess there’s some differences in how the key rings work, but Signal can figure it out and /they’re/ open source so it sucks they ever supported unencrypted messages. They just wanted to say it technically worked for rich text messages and reactions.