[jsmith45]

Yeah, while large portions of the online logic puzzle communities tend to agree that puzzles should not require backtracking (after all one can often trivialize the intended logical solve path like that), it has proven difficult to define what should count as backtracking vs a simple obvious contradiction that should count as a logical step.

Ability to visualize it in your head, without needing to copy the board, or make temporary marks is certainly not unreasonable for complicated puzzles. That is the same rule as Simon uses for logic puzzles (mostly variant sudoku) on the YouTube channel Cracking the Cryptic.

It isn't the most satisfying way to delineate the dividing line, since how much a person can track in their head can vary, but coming up with other rules can be absurdly tricky. Especially if one wants to make a set of rules applicable to multiple types of logic puzzles. After all simple two to three step contradictions may be unusually powerful for some types of logic puzzles, while they can be the basic deduction type for a different one.