Yes, I think here is at least one place the Amsoil bias enters in here and there's nothing a 3rd party can do to fix that. At least there's full disclosure on the apples to oranges comparison.
When I switched to the European Formula from Amsoil OEM (which I was getting cheaper than Rotella T6) I wanted to extend beyond the 3,750 OCI I had been following but refused to do so without UOA's. I went just under and just over 8,000 on the 2 changes before switching to their Signature Series, which is the same price (pay $20 a year and you get wholesale prices on everything, gallons of the SS/European are $30.65). My first UOA of the SS plus over-advance CEL's about the same time is what resulted in my long-awaited installation of my BNR 16g, IP&T oil line, etc. I'll be very curious to see the UOA upcoming in about 1k miles, now that I don't have a VF-40 with a stuck waste gate and the turbine wearing away at the housing.
If I can get my OCI up to a consistent 8-10,000 confirmed by UOA then I will be satisfied.