That was a stupid order that would never survive scrutiny under prior-restraint doctrine. Specific performance is something different, though... I can't think of any constitutional problems that might block enforcement of that.

Musk and his lawyers agreed to the provision, and a court approved the deal. That is pretty strong evidence it's not an absurd provision.

He has also violated it multiple times, with no sign of any consequences. That is pretty strong evidence that it was, at best, pointless.