Yes Yes yes  – the issue of femoral retroversion is real.  I for one was measured by 3D CT scan and found that my left femur is 20 degrees more retroverted than what is deemed normal.  This will cause boney restriction against internal rotation and increased range in external rotation.  The opposite is true for femoral ante version that is a boney block.  I understand one should not try to force past a boney/structural block as this will likely result in damaging the soft tissue/laburm etc.  If someone has extreme range in one direction and nearly no range in the other, there is a good chance you are dealing with a boney/sturctual issue and not strictly muscular one.