I think for defensive puzzles to really work better, the principle of what's counted as the right answer would have to be flipped on its head. Often in defensive situations there's one move that will end you up in trouble and a whole bunch of moves that will more or less avoid it. Picking what's the absolute best way to avoid the problem can be really hard, whereas just picking one of them is more straightforward. When it comes to attacking, there's usually only one way to get into the winning line, unless you're in an amazing position to begin with.