the first diagram shows the changes a custom tailor makes on his drafting system to accommodate the square shoulders. the made to measure change would be made on the cutting table. see how the gorge is dropped. today the lapel notch rides high. if the gorge were not dropped the notch would be on top of the shoulder. in ready to wear, the alteration is done to match those changes made on the pattern. plus the collar usually must be shortened. in altering, the gorge is not dropped. because the cost in labor would be horrendous.