Yep, most likely rejects.
Very damaging to a brand name if they don't destroy but dump the rejects on the black market.
I didn't expect the full 500F, and maybe a higher leakage, but these were seriously under-rated.
Still measuring, but most of them are about 100F, but with the leakage of a 500-1000F cap.
(they should leak less than 2.5uA per Farad)
There are some advantages over batteries. Potentially longer life (10-30 year), almost infinite number of charges/discharges, and low internal resistance. But indeed, you must use a boost converter to use them with electronic circuits. The NCP1402 is ideal, but no longer manufactured.
Leo..