OK. The BAA (British Astronomical Association) have been publishing their handbook for many years. It is published annually and is a highly respected source of astronomical data and used by astronomers the world over. In the back of the handbook (p114 of the 2020 copy) it has a list of astronomical and physical constants. The Earths radius (equatorial) is listed as 6,378,136.6m and the polar radius as 6,356,751.9m That gives a ratio of 0.0033528197.
Now that is pretty accurate and not the sort of figures that could simply be made up. I don't think the BAA is the sort of organisation to 'make things up' or deliberately deceive its paid members do you?
So while it is true to say that there is a degree of flattening due to the Earths rotation it is certainly not true to say that the Earth is flat. Of course if you want to believe otherwise then that is up to you but I would want to see figures from you to the same degree of accuracy that evidence your 'flat' Earth belief.
I don't know the methods used to reach these figures and I cannot make the measurements myself. However given the nature and stature of the BAA as an organisation I respect their quoted figures and accept them as true.
You can also find the data contained in the handbook here:
http://britastro.org/computing/pdf/Constants.pdf