I was reviewing this item, and it seemed to me that at one point the list of possible flag reasons came up without "very low quality" appearing, both in the queue and on the Question/Answer itself (flag link), but a couple of minutes later the pop-up did show that choice.
I'm inclined to think this might be an HTML fetch/timing problem, but previously I thought there might be some logic behind the truncated flag reason lists I saw occasionally. Here I persisted because the Answer had an automated low-quality score, and it seemed a natural option based on ambiguity of content.