[beart]

I think I might be confused by what you are stating. Are you saying it depends on your definition of "correct"? I think in this case, "verifiable" is what is meant by "correct", and in which case, if you can't verify it, by definition, it can't be correct, right?

[weinzierl]

Verifiable means you can find a proof that a solution is correct. I am stating that the effort to find this proof can never be more effort than constructing the solution in the first place.

I think where the line of argumentation in the article derails is that the author confused finding a solution with coming up with any odd candidate that could be a solution. The former is serious effort, the latter is trivial. Their Sudoku example is the former, their article example the latter