I mean, objectively, if you wanted to know the base oil viscosity (which is what Gokhan was trying to calculate) it's easy enough to do if you are the blender, since you know the viscosities of the bases used. It's no great mystery for those blending the oils.
The problem with trying to calculate it, as was observed, is that different base oils and VII combinations behave quite differently, so there's no accurate way to, as an outsider, work the finished product's data backwards to accurately arrive at that figure, hence it being only an estimate and an interesting, but not necessarily valuable, exercise.
I'm not sure of its importance. We have standardized testing for various conditions to establish limits and ensure compliance with those limits for wear, deposits...etc. HTHS is used by many Euro approvals and I suspect if there was actually value in knowing the base oil viscosity, they would be privy to that information as well. It's likely not on their radar because it's not important enough, and it can't be used as a metric to infer the performance of the finished product.