This isn’t going to be a productive conversation without proof. There is also the point-of-fact that if there was a NDA involved with said person. They wouldn’t be allowed to speak on it with anyone not listed. So we wouldn’t honestly be allowed to know legally without getting that admin in trouble.
Sure, they can approach any admin regarding federation. they still need approval of the Instance owner and the rest of the admin team as far as I’m aware.
I am curious though. Why not just join an instance that has already outright stated they will not federate with Threads?