It's very clearly not. Even if the Internet didn't exist, the data is there over the airwaves ready to be picked up by anyone with the slightest interest to listen.
Also notice how this applies to everyone, every airplane. Every celebrity, every politician, even every little private plane, even the president. Those are the rules. Elon isn't special and doesn't get special treatment.
> I think most of us would be uncomfortable
Uncomfortable, perhaps yes. But that's the price of being a celebrity. Paparazzi and all that. When you're unimaginably rich and famous, people track you. Happens to every famous musician, actor, etc. That's the deal. Elon doesn't get to be special.
Same thing if I put a tracking device on your personal conveyance.
AF1 routinely turns off their ADSB transponder, as do military aircraft. They generally do not when operating in high traffic areas, but will if they are over commercial airspace and want to mask their position.
While this data's purpose is primarily for safety and to make ATC job easier, it was never intended to used as a public tracking system.