It’s not just a matter of scale. I’ve been with tall girls that had deep but tight vaginal canals as well as short girls with shallow but very wide vaginal canals. (It’s a strange feeling to push all the way behind the cervix and watch her eyes rolling back in her head but to barely be touching the sides. I do love wide-hipped shortstacks.) Also with an extremely short and pretty heavy girl that was still very deep.
Doesn’t seem to be a hard and fast rule to it, but perhaps a correlation - just not enough of one that it’s useful to anyone. Finding out what they’re like inside in the first place is all part of the fun!