Just thinking out loud here, Michael, but I am wondering if the fresh application of the lubricant grease during a rebuild is not contributing a small amount to the separation of parts. When the lube is new and freshly in place you are creating a hydrodynamic film just from the viscosity of the fluid (grease) over which the parts can ride. Over time the viscosity can break down a bit and and also it gets pushed aside into the surrounding voids as pressure is exerted down on the moving surfaces. Whether the film integrity amounts to the size of the distances you are factoring here I don't know. A measurement would need to be done right after assembly, and repeated after some use period. After displacement of the grease you are left with an ultra thin film and relying more on the chemical nature of the additives over the original lubricant film volume. Or measuring the entire assembly clean and dry versus lube over the the working parts might show this difference. Maybe.
