In a greased bearing the problem is that the balls can touch each other (causing sliding friction) and /or pack together on one side of the race causing uneven

In a greased bearing the problem is that the balls can touch each other (causing sliding friction) and /or pack together on one side of the race causing uneven load or the inner race to shift relative to the outer. The solution is typically to put a cage in so they stay evenly spaced. This cage can be metal or plastic and the balls can rub against it. The grease is mostly used to lubricate the cage from the balls. The rolling resistance of the balls on the race is very low as they aren't sliding across the race, but _are_ creating friction and wear when they touch the cage. This system seems to work by allowing the bearings that are packed together to touch briefly as they enter the divot causing them to space out afterward. I guess it would perform similarly to an un-greased geared roller bearing? I'm not sure if this will work well under load. Grease provides lubrication to prevent pressure welding of the bearing to the race and it can also act as a heat sink. Besides those, I would assume the main problem would be fatigue at the site of the divot. Still I think this is very clever.