I think this is in part because the success of the fediverse is unique; its kinda the only post-web-2.0, genuinely community-owned platform that exists and has mainstream-ish mindshare.
So that success excites a lot of people, everyone wants their idea to succeed in the same way. So I think when they say "fediverse" in this context, they aren't actually talking about the fediverse itself as much as they are trying to reference its success and promise.
"Fediverse" just rolls off the tongue a lot easier than "self hosted platform that allows 1 admin to easily onboard 100 users, then form a resilient and genuinely useful global network with other servers while retaining autonomy on their own server"