The cutaway frame typical of a "girls bike" is structrually weaker (therefore heavier), but allows a girl in a skirt to mount the thing without violating modesty.
Modern off-road bikes have much smaller frames than road bikes, to put distance between the rider and the frame. Don't want to bash the family jewels any more often than necessary.
Women's road racing bikes are structurally similar to men's.
Oh...this is just effing ducky...now I’m gonna get a bunch of technospeak and excuses for what and why his bike looks like that...I’ll repeat again. Looks like duck, quacks like duck....etc. I don’t care about the specifics in this case...most men my age look at it and think ‘girl’. Don’t be offended.