I don’t consider being on Threads as being “on the fediverse”. My definition of the fediverse is servers that follow the Activity Pub protocol to interact with each other. You might disagree with that definition, but Threads only lets us “follow” (view-only) certain of their accounts (only about 2000 out of millions) from Mastodon. Those accounts do not see any replies to their post from the fediverse, or any fediverse posts at all for that matter–we are invisible to them. So no, he’s not “on the fediverse”, he’s on Threads. I doubt he knows the fediverse even exists.
Personally I hope they never do, though it does look likely. Like many pre-November '22 old-time Mastodon et.al. fedizens, I came to the fediverse specifically because I didn’t want to have anything with FB/Meta/Twitter or the other commercial, “engagement”-based, enshittified social media.
It feels like the fediverse is being gentrified, with half of it eagerly welcoming their new overlords (why don’t they just join Threads?) and the other half resisting. The half that doesn’t federate with Meta will move on, like people priced out of their own neighborhoods by gentrification, and become the new “real fediverse” where people can go to live free from corporate interference.