You still have to consult the state of multiple facet dropdowns, as well as the user's personal list of favorites at the same time to get the correct response, don't you?
As I said in my other answer: our facet filters are nothing more than hidden inputs in a form. So nobody consults "the state of multiple facet dropdowns", except htmx when it generates the URL of its XHR call. Everything else (filtering items according to querystring parameters, fetching user favorites, etc.) is done on server-side.