If you want to remember the population correctly, then that isn't a gray zone, that's an "again". That's entirely unambiguous to me, and if you let yourself slide on that, you're hurting yourself.
There's a lot more room for gray zones in language learning, where you might have the french card "doubler" and answer it as "to pass", and then see the actual answer is "1. to overtake, 2. to double", in which case you have to read your heart and decide whether missing the second definition was careless because it's so obvious, or if it merits an "again"
An AI also can't really know, btw, if your answer of "to pass" was "to pass (overtake)" (correct), or "to pass (like a note in class)" (incorrect).
That's not the best example, but there are a ton of ambiguous english words, and you only know in your own heart which meaning you meant.