[aerohead]

I think that they're just denoting 'separated/turbulent' flow around the aerodynamic system.
If the F-150 Lightning had been 'streamlined', and the gap was closed and 'tailored' to create an aerodynamic 'singularity', rather than the 'double-frontal area' structure we witness, then, we wouldn't see that 'disquieted' flow.
'Viking', behind 'Spirit of EcoModder' was striving for this 'singularity' condition, and creates a system clean enough that it at least compensates for 'being there,' not registering at all at the fuel pump. The same would go for at the charger with a BEV.
AeroStealth's IONIQ-5, if pulling Viking in California, would be returning 504-miles range, off it's 77.4-kWh pack, under EPA HWY-esque conditions. And this would be without the benefit of any onboard TT propulsion system.