A hermaphrodite is a plant or animal that has both sexes showin. (really simplified)
So in the world of hemp, a plant can start either way and later change, but to our needs you never hear of the male that goes the other way.
If a grower sees a male it will usually be yanked, and only a breeder might see this if they keep a male for longer than necessary to get pollen, and if it is found, it shouldn't be used for breeding.
Your concern as a grower are the females that grow balls, and most of the time this will occur between wks 4-6 (for an 8-9 wk strain) but can happen anytime.
I believe that genetics play the biggest role in hermi likelihood. With some strains you leave a door cracked once and you have balls, others won't change sides no matter how stupid you the grower are. (I prefer these strains myself)