It's a very long post, but a lot of it is a detailed discussion of terminology in the appendix -- no need to read that unless you're into definitional struggles.
I'm squarely in the AT protocol is not the Fediverse camp. Fine if people want to enjoy Bluesky, but the Fediverse is built on top of the W3C protocol ActivityPub. AT is incompatible. Cool that there's a bridge, but a bridge between incompatible protocols will always be a bit of a hack in my book.
"Anyhow, if Evan and Eugen and SWF and fediverse.party want to choose a definition of Fediverse where history stopped with Mastodon's 2017 adoption of ActivityPub, erases earlier Fediverse history, and ties the Fediverse's success to a protocol that has major issues ... they can do that. "The Fediverse" means different things to different people. It's still worth asking why they choose that definition."
You seem to be incorrectly stating what is on Wikipedia, which leads:
The fediverse (commonly shortened to fedi)[1][2][3] is a collection of social networking services that can communicate with each other (formally known as federation) using a common protocol.
That last bit is absolutely key: a collection of services using a common protocol. Imagine if two different email servers didn't both speak SMTP. Imagine if two different web services didn't both speak HTTP. The Internet as a singular entity is only made possible because of protocol interop between all of its constituent parts.
To say "the fediverse" is comprised of multiple incompatible protocols goes against that grain, and to go back to pre-ActivityPub-as-W3C-specification days as an argument that it's fine to label multiple incompatible protocols as all being components of "the fediverse" is a stretch.
To me, this isn't a let's-agree-to-disagree-issue, honestly. While the term "fediverse" is arguably colloquial and doesn't necessarily imply any specific technical attributes, it ceases to be useful as a term if Fediverse Platform A cannot in any way communicate with Fediverse Platform B because the two platforms happen to be using 100% incompatible protocols. Aside from a third-party bridge, the AT protocol used by Bluesky is 100% incompatible with ActivityPub used by Mastodon, Threads, and others. Therefore, they cannot both be simultaneously services in the fediverse.
For what it's worth, the guy who mostly maintains the Wikipedia page agrees with you. And yet even so, at least for now, the Wikipedia page states "The majority of fediverse platforms ... create connections between servers using the ActivityPub protocol" -- which pretty clearly implies that not all fediverse platforms use the ActivityPub protocol.
Anyhow whether or not you agree to disagree ... we disagree. Time will tell how broad usage of the term evolves. In the original article I pointed to examples of TechCrunch and Mike Masnick using the term in the broader sense, but maybe those will turn out to be points off the curve. We shall see!