How is the torso 'extremely' detached? When I try tracing the possible path of the girl's spine it looks like a gradual bend around 30 degrees toward our PoV. Then there is room for an arched back, leading to a raised ass that obscures the waist area behind it due the 30 degree bend from before.
She isn't perfectly aligned straight up with the guy below her but it seems like the intent was to have her in mid mounting preparation after pinning her love interest down, starting with the straddling action down below.