Probably mostly correct about that, but the possibility is there. I guess I picked a poor example. The flight to Qatar last week for the World Cup final would not have been possible and probably explains the most recent change dropping PIA. Flights over the Gulf from CA or TX to Florida also would not be allowed for a PIA registered aircraft. Flipping back through adsbexchange history shows a few flights that would be in violation if under PIA.
At the end of the day, they're going to be tracked regardless. There are only so many Gulfstream 6s flying out of the airports Elon flies out of, so PIA, changing the hex codes, etc., is only going to work so well for so long. Same thing with using a 3rd party call sign. Now instead of N628TS, it's DCM123 or some silly call sign, still the only G6 flying out of Brownsville. It's a little more difficult out of other airports, of course.
The real key is renting aircraft, fractional ownership, or even just using less high-profile aircraft. I bet there are a lot more Slowtation 525s or such flying out of Brownsville than G6s, but heaven forbid these rich folks don't fly on the latest and greatest.