Google’s extension of RCS does do e2ee, which raises the question of “what happens to security when you talk to a non-Google user”…

The fact that it’s thin and fading outwards makes it looks more like one of the crosshair options in FPS games

The real core difference is that XMPP just passes messages around (and history is just bolted on as an extra thingy between you and your server), while Matrix is literally a federated database of message history.