Yes, I understand the purpose, but I can't figure out how this rotation is supposed to be able to occur. The inner face of the thrust washer bears against the inner ring of the bearing, which doesn't rotate relative to the stub axle.

If the thrust washer was tightened so much that it was contacting the outer ring, then the bearing would have been horribly overtightened (they are supposed to have around 5 thou endfloat) and the bearing would overheat.

I suppose it's a belt and braces thing, in case the bearing hasn't been installed properly?

Tim H.
1986 4/4 VVTi Sport, 2002 LR Defender, 2022 Mini Cooper SE