This is probably a known issue, but I didn't see any recent mention of it.
For example, if I select "Pets with Unique Ability Sets" from the menu, I'm taken to a (super awesome!) results page. It would be nice it filter the list a bit more; let's say "Undead with Unique Abilities". And sure enough, at the top of the list is a link that says "Filter these results", which seems like it should fit the bill nicely. However, clicking on it only takes you to the standard search/filter page which draws from all pets, not just unique ability ones. On that page there doesn't appear to be a filter for unique ability sets.
It's fine if this is merely a technical limitation (e.g. unique ability sets aren't tracked in the database, and the menu item is a special custom query), but in that case it'd probably be best to remove the "Filter these results" option.
Thank you for the great pet resource!