Why would it be necessary to use Facebook dev tools for end users to interop with, and as described by the article, eventually migrate their personal Mastodon user endpoint to threads.net via ActivityPub and the data portability stuff?

I assume that most Mastodon instances are run by someone who wouldn’t count as a simple end user — but for the article’s purposes, the server operators are statistically irrelevant, compared to the majority of merely-users.