You can’t put wear on the ET2 spindle or bearing. The spindle can only be damaged by driving over it with your car. I realize that moving the spindle back and forth in the manifold feels “very wrong” and “rough” without the pump. It feels like you are damaging something. But you are not hurting anything and actually helping it if you can believe it. You are actually encouraged to do this a little on new arms to help them settle in.
If the spindle is so indestructible and tough, how can simply moving the spindle with no air benefit? The clearances between the spindle and manifold are set at the factory. You do not want to change the clearances. The arm is ready to go out of the box and requires no additional "fitting" by moving the spindle by the customer. That would be a poor design. I will be happy to eat my words if you can provide some proof that moving the spindle with no air does any good. Did Bruce say this to you?