No one is perfectly symetrical because we are one sided dominant. This dominance influences our pelvic position because of the uneven pull of the muscles on the attatchments.
It is a good idea to be aware of this and how the position of the pelvis has a powerful influence on the hip muscles.
You can stretch the muscles all you want but if the muscle patterns remain the same the pelvis will remain the same and nothing really changes.
It is ok to be a little different on each side unless you are striving for perfection of course.