They properly seat bearings. Both sides should be lubed with thick bearing or marine grease. Inner race washers prevent the shield from rubbing against the nut or axle. Aluminum is soft, so without an inner bearing, the inner race will dig into the hanger until it won't move freely.
It would seem better to stack washers on the outside. That said, I don't think three on the inside will hurt anything. After one session, half of one will already have dug inside the hanger.