Pabs, Since ASL,ATM,TSO seems to have a natural affinity to thickening in many applications I suspect that anything in a given engine that provides a little bit of anti oxidation solvency will help. Like;Ring seal, fuel dilution, fuel adds, oil adds, driving styles, oil consumption,etc.
Buster my friend, I won't speak to the comparison yet cause the fat lady of testing isn't finished.
The rise of any wear element is associated with the lubricants ability to prevent wear, increased vis by itself is not the reason for the increase, oxidation of the base chemistry in this application is.
Amsoil has a theory of formulation that is very different than M1 and we are seeing a good look at it here, keep going.
I say let brand bull stop by the way side and just look at this as two chemistries in the same engine perform in real time.
Call the oils M and A if that helps take the brand blinders off.
3MP doesn't look like a prejudiced tester to me.