This is all missing the point of why candidates get haircuts in the first place - to strip candidates of their individuality as part of teaching the class to function as a cohesive unit. You will probably be one of only a handful of women in an otherwise predominantly male class. While it's a seemingly minor symbol, the fact that your long hair is wrapped neatly in a bun while the men around you are bald with scratches no longer makes you the same as them, in both their eyes and the eyes of the staff. On one of the first days of training, your experience will already be different from theirs - you will not have sat in that chair for 10 minutes while some disgruntled barber takes a sharp object and digs it into your skull to the point that it scratches you, while simultaneously still managing to miss spots.
I personally think that teamwork lesson is far more important than sparing you the trouble of finding an ENS/LTJG 6-12 months after graduation and whispering "hey, about that bun...how do you actually do that?"