Quick questions often require the longest answers! The short answer is, “yes!”
For the full answer, I suggest you look at pages 110-114 and 124-151 in
Your Body, Your Yoga. In general, femoral torsion can limit rotation of the neck of the femur in the hip socket due to contact (impingement or compression) between the neck of the femur and hip socket. This can happen in standing (hips neutral) or sitting (hips flexed). A femur with high rotation (anteversion) can internally rotate more than a femur with low rotation (retroversion), but higher anteversion can reduce external rotation while low anteversion (retroversion) increases external rotation. Generally, this effect is maximal when the hips are in neutral (i.e.: standing) but the more you flex your hips, the room you have for external rotation. You may find that you can externally rotate easier when you are sitting than standing, and more when folding forward in sitting than sitting upright. For example, notice how high your knees are off the floor when you sit tall in Butterfly compared to when you fold forward. The increased hip flexion gives more room for the neck of the femur to externally rotate before it impinges on the rim of the hip socket.
Again, see the book for the gory details as to why.