Anatomical variance

Looking at simple anatomical variance, there can be a massive difference between individuals in the shape, alignment, positioning, and relative angles of attachment of specific bones and joints, meaning their ability to move will be entirely different than someone who has a different set up.

References:

https://bretcontreras.com/no-two-hips-are-the-same-how-anatomical-variance-can-affect-your-range-of-motion