The Earth is an oblate spheroid.
The Earth has a slight bulge around its equator due to its rotation.
https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Equatorial_bulge.html
This isn't correct, even if RET were true. If the Earth were a sphere, its rotational velocity is not high enough to create a oceanic bulge that could classify it as something other than a sphere. While it is not a perfect sphere, it is closer to the defined properties of a sphere than it is to the defined properties of an oblate spheroid. It's like taking 0.3 and saying it would be better to round it to 1 than 0.
Measurements point to it being true.
So... who to believe? Someone who simply cannot think or a scientific measurement? I choose the scientific measurement.
Whether or not the bulge is significant or not, it is not a perfect sphere. A difference of 42 kms is pretty small on a planetary scale, but certainly seems large enough if you were to go out and travel 42 kms.
Your analogy of rounding 0.3 to 1 instead of to 0 is an inaccurate analogy.
An oblate spheroid is a rotationally symmetric ellipsoid having a polar axis shorter than the diameter of the equatorial circle whose plane bisects it.
Because the difference is only 42 kms does not mean that the definition is moot.