Fairly certain I've gotten some "Not HQ" results from airships that were, in fact, actually HQ items.

I think that "Several HQ" means that you can exceed your normal gathering quantity.

I've been putting whether or not the items found were HQ (Vivianite HQ, for example) in the log but, as you said, you have not been actively tracking that. I think you probably should start, if only to disprove the theories regarding non-HQ, HQ, and Several HQ and how they correlate to what is actually found.