They consider 6.78 w/kg if pogacar is 66 kg.
If he was 64/65 kg is probably around 6.8 w/kg.
Since they do in standard weight 70 kg to compare the perfomances of riders with different weight, they consider Pogacar did 6.75 w/kg (473 W/70 kg) and Vingegaard 6.61 w/kg (463 W/70 kg).
I swear; I did not come up with those calculations!