Ah, I understand (or at least I think I do - the 'rule').
However, the way I saw it, the slope in the rear of the cab didn't violate the shape or the respected drop-off angle(s), thus the Denali should in all fairness have attached flow at least as far as the C-pillar.
Thus if one then 'cheats' this ideal shape forward (to match the already gently sloping roof), the canopy/cap could loose another hand-width -or so- of height right at the back because the angles are all still good, Hence, this reduces the size of the wake, quite possibly still without the risk of detached flow compared to where the shape should 'ideally / per rules' sit.
Ignore this post if I'm just not getting it
