It's not that they're "cheating". It's just that many problems (like this one) are only difficult under some constraint. Lift that constraint, and it's easy (and therefore uninteresting).
I'm absolutely certain that Feynmann himself discovered the same thing as I did many decades ago, and that he discarded this "solution" because it was outside of the constraints that made the problem interesting.
I'm absolutely certain that Feynmann himself discovered the same thing as I did many decades ago, and that he discarded this "solution" because it was outside of the constraints that made the problem interesting.