Another way to look at it is that tracking what you eat is very difficult. Currently trying to lose a few pounds and doing calorie tracking. Practically carry a scale and a calorie tracking app with me. About once a day there's still some "estimation" involved due to the fact that all the ingredients are mixed together.
Indeed. I also tracked everything I ate for a long time, many years ago. As soon as you eat something made by someone else you're basically guessing.