As one of the chairs of the Open Metaverse Interoperability Group and a member of the Metaverse Standards Forum, "metaverse" is a term with a ton of baggage and not one we really like to use internally at Matrix. However, it's also the one people know the most right now :( Multi-user interoperable virtual worlds doesn't quite flow off the tongue and immersive-web or wider-web haven't really caught on outside a developer audience. Maybe cyberspace will make a comeback?
Also, more importantly we don't believe in "a metaverse" in the same way we don't say "an internet". There's only one "metaverse". Open and interoperable should be baked into the definition. Matrix can play one part of it.
The marketing about it being a "metaverse" seems misplaced even if its technically true or not.