The aircraft tracking data itself is public, but what's not public is the information which links the temporary aircraft identifier to its owner when the owner is using that privacy program, which is the case for Elon: https://twitter.com/elonmusk/status/1603803508087537665
That source is a reply by Musk confirming a statement by another person (https://twitter.com/Timcast/status/1603748611896283137?s=20&...) commenting about Musk being enrolled in the PIA program. That statement also has a link back to the creator of the tracker themselves also admitting Musk's plane(s) are/were in PIA but they figured out how to track it/them anyway.
But it's not public information by law. It's private information:
https://www.faa.gov/air_traffic/technology/equipadsb/privacy
The aircraft tracking data itself is public, but what's not public is the information which links the temporary aircraft identifier to its owner when the owner is using that privacy program, which is the case for Elon: https://twitter.com/elonmusk/status/1603803508087537665