it's not technically a bug which is why the item type filter is definitely not coming back haha. the "type" of the item is really just an awful thing to filter by because every item really has like 3 or 4 types it can fit into and the item admins just pick one when they add the item. the type filter has nothing to do with rarity and ONLY checks the item's specified type (which is the same thing as its category would be in the inventory if you have "show categories" turned on wow why do we use different terms for the same thing that's so not helpful to anyone).

there is an item use filter, which sounds kinda like maybe what you're asking for with the collections filter, and afaik it works. i know it was broken for a while due to some changes in php parsing when we upgraded our version of php a while back, but i believe it was fixed a few months ago.

but again, the item type filter technically isn't broken, because it correctly filters by the type that is assigned to the item, which is what it's supposed to do. it's just that item types are largely useless :P