It’s a measurement of energy needed. Bodies are going to take different amount of force to move the thing, but it’s also going to take a different amount of time, and impart less inertia.

Measuring how we consume our calories is also a bit tricky, the bike tells you the minimum energy you spent moving the wheel. It could be slightly more, but not by much because our bodies are pretty efficient at using stuff to burn into energy. The amount needed to move the bike is about as much as we’ll burn because there isn’t a lot of waste. Of course if you have a condition, or are out of shape this changes and the counter becomes more inaccurate.

We still calculate how much calories are in food by burning them and seeing how much energy they emit (heat). It’s not really how we consume calories but very similar.