'Potential' isn't the same thing as actual scores received and known, especially not when we're talking about Grace McCallum. Skinner's overall scores in Tokyo were higher, this is just a fact. 7.1 beam execution score and all. That's the best data we have.
Even then, there are three events not four, so why are you excluding one? By the same token, we should give equal airtime to a hypothetical that excludes beam. And actually that would make more sense, since the 4th was always more likely to be used on vault than anything else given Suni's strengths and injury.