First image "Moi" smoothing
Second image Global Phong smoothing

Real time engine = low poly
infos given by original Moi's normal help to simulate a virtual smoothing by light's modification and not physicaly by polygon :)

in case of "wrong normal orientation" global Phong don't enough sufficed : if low angle for have good straight edges but lost smooth on curves (and defauts of ngon topology or triangles)
if hight angles straight edges are "smoothed" !
So "circle's squaring" if inverse normal is not making in moi ;)