That's a good question. Except some of the darkest ones I have have it too... Plus I have seen some males (adult) get it - though more visually on dark bodies than the light ones.
Ventrals: all are the same size to me xD in comparison to the same sized fry.
But if the stripes were a sign 50% jarred would be females (and mean ones a that) ill try getting a pic of a bully I pulled two days ago. Has some regrowth of the anal fin, but has the longest fins so far out of these fellas.
Breed for the breed, not for the money; the words any REAL breeder would understand.
You must know nothing in order to know all, for all is nothing and nothing is for all.