Waton- yes more us vs them, exactly what we need - let the name calling begin!
If you are talking about Eratosthenes, his measurements are just measurements. What they mean is a matter of mindset. If you are a rounder, it means the earth is about 250,000 stadia in circumference. Conversely though, to a flat earther, it means that the sun was at a particular distance away from one point that was measured, and a different distance from the other point giving a close sun and flat earth. You can't prove either POV from just the measurements.
Its bad science to draw one conclusion from measurements that have more than one interpretation. Eratosthenes did this. Many today do this but it's still bad science.
Add it to your supporting evidence of you must but it's not proof. Not for either side.