ActivityPub, HTTP, XMPP, etc sound like technical things. If you land on a page talking about the "XMPP specification" then you quickly get the idea that it's not where you want to be as an end user.

"Matrix" does sound a lot like the name of an end-user relevant product of some sort, and a client sending users to matrix.org compounds the issue.

There's a reason why big companies have brand guidelines. They have people on staff that understand that people are confused quite easily and don't want to figure out where "Matrix", "Element" and "Element X" stand in relation to each other.