This is it. There will always going to be impossibly unpredictable errors even if you measure everything perfectly.

The point of measuring is to be * as accurate as possible *, not 100% error-free. It helps to better estimate portion sizes, calorie / macro amounts. This is enough precision to control weight gain / loss correctly.

A lot of people also get their maintenance calories estimation wrong, so it doesn't matter if you can measure your food down to the molecules but still eat too much / too little.