Yea, when I saw these limitations, the first thing I thought of was Tesla. And Tesla makes it very clear with their messaging, when you first pair your phone, something like 'Due to limitations by Apple, you won't be able to participate in group chats.'

It seems obvious to me Apple always wants to keep one critical thing inaccessible for iMessage, to lock people into using their platforms. They'd rather Tesla use car play, that way they can lock the integration down so others (like Windows) can't use the same integration.