Let's back this up a bit here, because it's your wording of the first bit that caused me to address your post and provide the examples I posted.
You stated:
Pretty straight forward. This stands on its own as a statement made, without qualifiers, that a 5w-30 will always have more VII; will always be inferior to a 10w-30. You've left no room for leeway in this statement. Are we in agreement on that in terms of how it is worded?
On to the second point.
You then follow it with the qualifier:
This in no way reels back the absolutism of the first statement or implies that the reader should assume that there may be myriad exceptions to the first statement because you didn't state that:
All things are almost never equal.
Which is why I responded. Fair?
As you are aware, oils are formulated to a performance and price point, two things that are interdependent. If your performance point isn't that high because the grade doesn't have to pass stringent approvals, it's going to be a cheaper blended product.
The Mobil blending guide excerpt I posted shows some examples of "ideal" formulations where you can clearly see that the 0w-30 has more VII content than the 0w-20, which certainly supports the "all things being equal" premise, which I I have no issue with. But in application, those oils aren't going to be blended that way.
I didn't read what the OP asked as saying "if all oils were blended identically in terms of basestocks, why wouldn't I just use a 0w-30 or 5w-30", but rather, was asking about the spectrum of modern oils, which brings us back to my answer, and that is simply that it depends.
We have oils of the same grade that vary WILDLY in formulation (TGMO vs M1 EP 0w-20 for example), base selection and VII content, so I tend to object to making broad generalizations based on parameters that will never be constrained in the idealized manner presented in real life.
If we look at two Mobil 1 products from the same family, say Mobil 1 High Mileage in both 5w-30 and 10w-30:
View attachment 86124
View attachment 86125
With the limited information we get on an SDS, we can still see that while both have PAO in them, the 5w-30 has more. Now, we start going across brands and we'll find zero PAO in either of those grades with many of the brands, while if we go to a lube like Ravenol, all of a sudden it's majority PAO.
Does that help?