I'm just working through some flags, and I notice that some answers allow a choice of NAA and VLQ (among others), but some particular questions don't allow VLQ.
For example, for this answer, which I think shouldn't be "Not an answer" (because it is, it's correct, it's just very poor on content), so I'd like to flag it as "Very low quality". However, the flag options I'm shown are just these:
Where has the "Very low quality" option gone? It's ok for many other answers.