While I'm sure Threads as a whole is an attempt at EEE, I don't think this is that big a deal. In fact, I'd like to see every other site support it, too

As the article mentions, verification on Mastodon is just verifying ownership of some links in your profile (not the entire account), which just checks the target site for a special link back to your profile (specifically adding the rel="me" attribute to it). Now when you add a link to your Threads profile, if it sees a rel=me link pointing back your Threads profile, it will add the rel=me on its end as well. Following the steps in the article, Mastodon will then see the rel=me attribute on the link to your profile there, and show the link as verified, just the same as if it saw any other rel=me link on any other site. And any other site that supports link verification the same way will also now be able to verify ownership of your Threads profile.

Using rel=me links like this is a great simple way to cross-verify all your other accounts and websites without needing to sign in or authorize any access. Just point the two sites at each other and violà!