I would agree with you but unless I'm totally remembering the conversation wrong, TT said he could spin faster with the longer crank. Sheldon certainly advocated for shorter cranks, with this in mind. The thing is that with mechanical advantage it doesn't really matter how fast you can spin, what matters is how fast you can move your feet. If you can move your feet faster in fewer big circles than in more smaller circles then you need a longer crank and vice versa and the biomechanics are not transparently related to leg proportions.