Vertica Place creates circle-like polygons with vertices not equidistant to the center

Hello, I'm in the need to design a solution that requires precision on geometrical/geographycal operations.

Creating a circle I realized that the resulting polygon has vertices with distance to the center with an average of 15% less of the correct value with a peak of 30%.
Also the circle area value is different to the value I expected (217km2 vs 314km2)

I'm using the following statement to create a circle around a geo position with a radius of 10km:
select st_astext(st_buffer(ST_GeomFromText('POINT(9.0004 45.9997)'),0.09));
considering 1 degree = 111111 meter (as simple as earth circumference divided by 360)

Find attached the completed analysis.

Anyone can tell me what is wrong in my analysis?

Thanks in advance,
Vivian.