I think that's fairly common in individual competitive dance. I assume it's based on the range of moves that breakers can do or not do based on anatomical limits, but I don't really know why. I can't think of one breaking move that one gender can always do and the other always cannot, not an expert on any of this.
I was uncomfortable with the way they call the breakdown, b boys. And b girls. Just call it women's and men's, if you're gonna do it, IMO.