"Knowing when the math is hard is way harder than the math itself"
But then maybe the math is hard only because it's not being explained well? (I hope it's uncontroversial to suggest that our current methods of teaching math are not the best of all possible worlds.)
I get that this problem came up in the context of of a math puzzle contest, and that some people enjoy solving puzzles. I am questioning their utility as an educational device.
I kinda think that we should teach math as fast as we can so that we can concentrate on the stuff that's really hard, not just apparently hard because someone is being coy with the easy routes.