You don't believe that homind cranial enlargement is responsible for more than half of the difference between modern humans and dogs, so why does it matter when it happened?

Suppose that dogs are 50-100 times further away from humans than chimps are. Further suppose that bacteria are more than 100 times further away from humans than dogs are. Why is one of those a reason to include chimps, and the other not a reason to include dogs. (Rocks are more than 100 times as different from humans than fungi are, right?) Rather than use relative closeness, I'm going to assert that absolute distance is important. (If that means that a typical human 400 years ago would not qualify now, I think it says more about them than it does about me; but I don't think that is the case).

I also danced around and didn't actually say that 90M:400 was the best prior; I said if I needed one quickly it's the one I would use. To refine that number first requires refining the question.