^
Typically when a single page goes deleted in a pool for quality reasons (when the rest of the pages can't redeem it) it also means the rest of the pool has to go since the overall quality is bad. I'm sure NWS knows more about it, but any error present in a single page for a multi-page will usually also be present in most if not all the rest of the pages in it.
And yes, that thread is simply for flag vandalism, this is a different concern (since all the other flags are valid). Well, at the very least you learned something about how appeals get others' attention. There's always the chance that once an artist's work is flagged, the rest of them, if they're of the same/worse quality, usually follow in turn.