Common Ground and Video Ground on JAMMA/MVS. Are they the same?

[RealMFnG]

Are they the same? Bought a cheap supergun for test bench purposes and am finding that Video Ground and Common Ground have the same connectivity. Is this correct?

 

[nem]

No, they're not the same. It depends on the PCB. On cab harnesses I would never tie video ground to common ground. With bootleg boards that don't have video ground connected, I add a jumper wire.

As for the supergun, if it works, leave it as is.