Matrix, while kind of a PITA for non-technical people to get into, can do it quite well considering the featureset they support.
In other words, it has a bad UX. Which was the original point about encrypted group chats.
If one app found a way to make a nice UX for it, all the others would follow. So in practice it seems perfectly reasonable to say "Matrix" when talking about the general UX found in apps implementing the Matrix protocol, doesn't it?