This isn’t entirely true. Verification on Mastodon isn’t verifying your account for a shiny badge, it’s verifying ownership of sites that you link on your profile. If you add a link to a website, and that website links back to your profile, Mastodon will show that one link as verified. But that link needs a special rel="me" attribute to count for verification, which is what Threads now supports.

I am absolutely sure Threads is an attempt at EEE, but this specific feature is a good thing imo. I’d love to see more sites support rel=me links for simple cross-platform account (ownership) verification

This isn’t connecting to ActivityPub any more than putting “rel=‘me’” in the head of an old Blogger blog is.

I guess the real question is this is “why?”. If they’re truly planning on federating, this is the equivalent of having your mastodon.social account show up as “verified” on your mastodon.world alt account.