He thinks he proved addition with his example. But he didn't, because math was necessary for him to do what he did. He says, put two apples in a pile and add two apples to the pile. They are logically prior to the problem. Again, I agree that math is objective truth, but not because it has been proven by science.
Nobody does that.
Science doesn't work that way. You have to do dozens and dozens of experiments, and many other people have to do their experiments to prove a universally true scientific principle. It is obvious that it's always going to be the same. You know this to be true before you do your experiment. That's why your experiment works.