I've lapped two uppers. One barely needed any lapping at all. It still has some anodizing left but it is visibly thin. The other needed more lapping to even up the receiver face. It now has a distinctive half-moon look to it. A third receiver (Precision Firearms) was so tight my lapping tool wouldn't fit in the carrier channel so that one went un-lapped. I clamped the receiver vertically in a vice with a bubble level centered on the face. I rotated the level 90 degrees & the bubble was still centered. It obviously didn't need lapping anyway. I had to warm it a bit to get the barrel started. This same barrel rattled around in the receiver (BCA) it was in before.
I refuse to be victimized by notions of virtuous behavior.