wow! i really would like to know where you got this information, or who fed you this lie. all my i have never had a trainer, physical therapist nor any training book or website provide such inaccurate information. don't you think the guys in the military who are required to x amount of pullups would stop at 90 degrees of elbow flexion.
full range of motion is the only way to prevent injury and increase size and strength in the lats.