Greasing the ball is a good thing. Especially when using a WDH, where the forces on the ball are much higher than normal. Without it there can be a lot of galling and rapid wear.
When using an Anderson WDH, the ball turns with the trailer tongue, but the flexing over uneven surfaces concentrates the wear on a very small area of the ball. This leads to severe wear spots from an imperfect sperical shaped coupler socket.
Anderson used to say no grease was needed, but when myself and a number of us pointed out to them the wear and noise problems associated with the extreme load, they changed their tune and began recommending grease. Why do I keep getting the idea that Anderson is just winging it? The Anderson hitch also has a different force angle on the ball than a conventional WDH. The Anderson pushes forward on the ball for weight
distributing, instead of the regular straight down load applied by systems with spring bars. This means the force is on the coupler's catch mechanism in the coupler, instead of at the top of the socket. I don't like this system and if used, one should use a Bulldog coupler because they are so much stronger with a forward load. Tremendous force on that little catch mechanism of conventional couplers is not a good plan.