There are variables that cannot be accounted for, and that small of difference is very small indeed. Even air flow can account for that variation.

As filament is extruded it expands to a larger diameter than the size of the orifice it is being pushed through, this happens with all plastics, at all stages, whether it is during the making of the filament, or the printing of a part. That makes calculating actual usage very difficult at best. Your discovery is still something that is helpful, as it lets us be aware of possible hang ups from distorted filament, and other problems that may arise. I would have never even thought to look for out of round filament. I still thank you for your discovery !

Your filament is probably of high quality, I did not mean to imply otherwise. Home made filament can be as good, possibly better than factory filament, depending on the reliability of the supplier. You definitely know what you are doing, keep up the good work. Your contributions are greatly appreciated !