Speaking as a electronics design engineer for high end satellite communications gear....
None of the SS pinball manufacturers had good grounding schemes, Gottlieb was the worst with their System 80.
Their model 3's improved as the 4.2mm connectors were a tremendously improved connector. Their grounding scheme still sucked even though the connectors were better.
Nothing beats a screw terminal for good grounding. Crimp terminal, heavy gauge wiring and ground screws can't be beat.
With 50/50 hind sight - would have been nice if all of the boards (regardless of manufacturer) had a ground screw connections and a proper grounding scheme (e.g. star ground). Terminals with screw connections for high current power as well - no more burned connectors on power supplies! But they went for the high profit/short life span design... and I sell tons of replacement power connectors as a result.