ex: https://flightaware.com/live/flight/N330AX
Are these planes sending bogus data (like shifted by a tens of miles ?) They are old Archer Hunter planes (apparently) owned by some trust., and two of them seem to have flown very close together.
Their ownership is obscured via the TVPX trust company, but they're really operated by Airborne Tactical Advantage Company (ATAC): https://atacusa.com/
This sort of training happens all the time, and you get used to seeing lots of aircraft circling around over the ocean in southern California.
Edit: Right now in that area I see aircraft from at least two other contractors that do threat simulation for military training, plus an unknown military aircraft. Sometimes you can check the AIS tracking sites and see military ships in the area, too.
It's not surprising that it's owned by a company nor that it flies in formation with similar aircraft.
Flying an airplane like this over water for noise abatement purposes is also common, because they're really loud. The flight path looks like airshow practice.
Some older planes don't have GPS enabled transponders so they can only be accurately pinpointed when interrogated by radar. To get a fix tracking networks will calculate the time the signal arrived at multiple receivers and work out the math to ballpark the location.