Most people assume that more balls is better, but that isn't necessarily true. If you look at this heavy duty industrial bearing you'll notice that there are fewer balls used than possible, separated a bronze retainer. This is a common design. I assume the makers and buyers know what they're doing, and want good quality, load and wear characteristics, and aren't trying to cut corners by skimping on balls.

This isn't offered as a technical explanation, but just to show that more isn't necessarily better.