Android users still go on WhatsApp for group chats instead of using RCS. I'm in an RCS group chat with some Android users, and they're always missing messages even between each other. So no I don't buy it. Same with MMS, Google and other phonemakers always blamed Apple, but nobody actually wanted to use MMS even in a full Android group chat.

Maybe RCS between Pixel phones is ok, because that's not the same thing, it goes through Google's servers only. And that was also the only way you got E2EE in RCS until very recently.