Please tell me because I just failed a reopen audit on it! :-)
I believed the purpose of audit questions is to correct "robo-reviewer" behaviour. If that is true, then I don't think that was a good audit question.
A conscientious reviewer (which I believe you were) could decide that question should be closed. Whether or not that close decision is considered correct, the point remains that you reached it by thoughtful deliberation.
It just seems wrong to me that you should be presented with a fail notice which screams at you to slow down and pay attention. If your "leave closed" decision was actually wrong (I'm unconvinced about that), it was not because you were whipping through the queue too fast. If audits are intended to discourage robo-reviews, the audit questions should be more clear-cut.
On the other hand, if audits are also intended to train us about nuances of close vote policy, then maybe it was a good audit question after all. I would have failed that audit same as you. That means I don't understand close vote policy well enough. And that makes me conclude I should stop reviewing reopen and close votes.