Why it matters
A distributor's "hydraulic hose fittings" category page with a real selection guide and links to subcategories gets cited. The bare faceted-filter version, just a grid of SKUs and checkboxes, does not. An AI engine retrieves passages. A category page that is only a filter UI has no passage to lift, so it stays invisible in answers even when the catalog underneath is complete.
This is the e-commerce SEO topic of taxonomy structure, with the AI-retrieval cut added. The question shifts from "does this page rank" to "does this page contain a quotable, self-contained chunk an engine can attribute to your domain."
Content-bearing vs filter-only category pages
Filter-only: a results grid, facets for thread type and pressure rating, no prose. Nothing to retrieve.
Content-bearing: the same facets, plus a short selection guide (JIC vs ORFS, working-pressure ranges, how to read a dash size), named subcategory links, and a few canonical part numbers. The page now holds chunks worth citing.
In practice
Take a category like "NPT hydraulic adapters." Add a 120-word guide that defines the standard, states the size convention, and links to the SAE and BSPP sibling categories by name. Keep the facets. You have not removed the buyer-facing filter. You have given the engine a passage to quote and a reason to name your domain as the source.