Thing is that you dont have to formulate hypotheses for things we have figured out. We, humans have already figured out for example that momentum balance holds,

Thing is that you dont have to formulate hypotheses for things we have figured out. We, humans have already figured out for example that momentum balance holds, so when we make trajectory predictions, this (differential) equality is a hard constraint in our calculations. A DNN cannot guarantee that its predictions respect momentum balance. By proper training you can just only reduce the probability of violating it. It is plainly a wrong tool for the task.