There have been many published studies that conclude that cup placement is a key factor in MOM wear. If the cup is placed too vertically, the cap rubs against the upper edge of the cup, referred to as edge loading which leads to excessive wear. If the cup is placed properly, the cap rests against the smooth interior of the cup, instead of rubbing against the sharp edge.
There are certainly other factors that may affect how a persons body responds to the wear debris. There are other factors that may affect the amount of wear, such as design and metallurgy of different brands, but I believe that extensive studies have made it clear that edge loading due to poor cup placement is a leading cause of high wear.
I would like to give this doctor the benefit of the doubt by considering that you might not have understood him correctly. If you stated his position correctly, I would look for other opinions elsewhere.