Sorry, I must admit to not reading the OP before replying. Not sure what the OP is on about; of course both surfaces wear, the important thing is the sequence

Sorry, I must admit to not reading the OP before replying. Not sure what the OP is on about; of course both surfaces wear, the important thing is the sequence of which surfaces are compared/lapped against each other, and how they are oriented. The orientation is quite important - if each pair of plates are always at the same orientation relative to each other (or I suppose 180 degrees from that) then the plates may meet evenly, all having the same twist. Foundations of Mechanical Accuracy is a great book if you're in to this sort of thing.