It's simple ! Strictly looking at it from equal prizemoney perspective, either the ladies go B05 or the Men go BO3 !!!
When you also factor in how slow the modern game is played these days as opposed to the 1990's and 2000's , what with slow tennis courts, MTO's becoming frequent (some questionable one's) , Ninety percent play from the baseline, and that there's no more tournaments has BO5 outside of the GS, (Davis Cup was the last one to be phased out),
you could argue B03 for mens and womens in early rounds, up until the semifinals and finals, then it's BO5.