i partially agree with the above openion
during protraction there occurs mild flexion at the lower cervical area,more flexion is at the upper thoracic segments.the upper cervical spine is in extension and there is also anterior translation of upper and middle segments (jutting)
and during retraction there occurs extension of upper thoracic,neutral-mild extension of lower cervical spine,upper segment can even in mild flexion,neutral.
since retractors and upper cervical flexors has more chance of being weak they are emphasized to strengthen simultaneously.
we will be doing a bit of over correction ,so that the posture becomes ideal in preventing postural related contribution to cervicobrachial disorders
this is my openion and expecting to see others perspective