Bob, the GC's that I play on can hold 8 balls, though i like to remove some when playing one pocket. But they can hold 8. I don't know what GC's you're playing on. The equipment in the room I play in is kept top notch and never noticed anything like you are talking about.
Maybe they got better pocket liners. The standard pocket liners for non-return GC3 tables are shallow/small enough that if there are three balls in the pocket, there is a good chance that a hard shot will reject the ball. I've also seen a ball rejected when only one ball was already in the pocket as it sits centered in the drain hole and can push back on the new ball hard enough to send it back onto the table.
A story about the latter... Around 1979 I was playing Tony Annigoni (of Playing Off the Rail fame and noted tournament promoter) on a GC (probably 2?). Whenever he had a fast shot into a pocket, he would make sure there were exactly two balls in the pocket. I thought it was craziness at the time, but it was a smart move learned from hard experience.
Other misfeatures of the GCs:
Metal parts on the rails to leave oxide streaks on your pants.
Prominent name plate and score wheels to take flesh off your knuckles in case you try to keep your cue level at the wrong time.
No slate pins (GC3)
Lousy ball storage that allows balls from my side (1 pocket) to move through to my opponent's side (ball return table).
Pocket liners and metal surrounds that screw with your bridge
Diamonds you can't see when you are down on the shot due to the curved rails. I think the curved rails were a "feature" to roll cigarettes onto the floor away from the cloth.
Lousy rack hanger. (A local room has added their own.)
The Diamond design appears to have taken all of these crappy points into consideration and fixed them.