I was talking (on Facebook) today with the previous owner (actually his son, who did most of the driving of the Jeep). He said that when they bought the Jeep, three of the four wheels had the brakes packed with grease.
When I assembled my rear axle the other day, I did it such that the extra hole in the retainer plate, all the shims, the brake backer plate, and the grease retainer all lined up. The "grease protector" doesn't have the extra hole, but it has that hump in it. I figured the purpose of the protector is to help direct any grease coming out through the seal to go down the hump and out through that extra hole. (Whether that thick grease would do that instead of going onto the brakes is a different question.) Did I figure right?
If so, one must presume that whoever owned it before the guys I bought it from must have had something assembled wrong, and/or were waaaaay to aggressive with the grease gun!
-Paul