Here's the same polygon sphere with different subdivisions in the
height and axis.
Inputs
polysphere
Subdivisions Axis 13
Subdivisions Height 13

Subdivisions Axis 12
Subdivisions Height 13

Subdivisions Axis 12
Subdivisions Height 12

It seem like there's a threshold before the smooth shading turns to flat shading. Is there some way to increase it? Or is there another solution to my problem?