Personally I think it is fairly easy to answer this one.
Most ABDL tent to empty up our Blatter in one go while diapers are made for incontinent people.
Incontinent people unusually loose smaller amounts of urine but more frequent.
Diapers need time to absorb and distribute.
But I do agree that the female anatomy is better suited for diapers they start to distribute their urine from the center outwards while most man start from the front.
Therefor the front panel can be fully saturated while the back panel is still dry.
This being the case the diaper might start to leak on the sides while the rest is still unused and dry.