Agreed, which is why I shared the Australian doc to begin with.This whole thing grew out of the whole "0W-16 oil is a must", argument. It is not a "must". The U.S. manual only states that it is "preferred". It also states that using an oil with a higher viscosity would be better suited when running under high speed conditions.... Which makes sense.
The only tie in with 0W-16 in the manual is to, "better fuel economy", and "easier cold weather starting".
I think what we're all shooting for here is that "better" solution that makes more sense for the majority of drivers...especially compared to what the factory is recommending, which is obviously biased towards CAFE standards for the most part.
I'd venture to guess that "the best" median UOA values would likely come from 0w-20 or 0w-30, or heck, combination of the two. We all know that Toyota's aren't exactly hard on oil, but given the choice, the higher viscosity would likely do more good than harm; especially given that a good amount of drivers fall into the "severe" maintenance schedule without even realizing it.