What if Meta identifies a user on Threads and/or Instagram (who has therefore agreed to the TOS) using a pseduonym on a totally arbitrary Mastodon server? All

What if Meta identifies a user on Threads and/or Instagram (who has therefore agreed to the TOS) using a pseduonym on a totally arbitrary Mastodon server? All Meta has to do is drop a little sidebar on that person's Instagram profile that says "This user also identifies as XYZ@server" Person has been doxxed, the content is entirely on Threads or Instagram , they agreed to the TOS, and it seems very plausible Meta would do something like this.