Questions can be pushed into the Reopen Votes queue either by an edit or a reopen vote. As you said, the only revisions were made by you after you saw the review item, so that couldn't have created the task. I see only one reopen vote on the question now, which I suspect is yours, again cast after you saw the item. Therefore, the question must have only been shown in the queue as an audit. (Also, I'm fairly confident normal review items do not transform into audits mid-flight.) The system likely chose it because of the low score and closed status.

Had you used "Edit and Reopen" *from the review page*, I think you would have passed. The "correct" decision had already been decided when the audit was created, so your edit outside the task didn't change anything. This is unfortunate, but since you're clearly a conscientious reviewer, there's no need to worry about failing the occasional dubious audit.