> A prefilled list is never an acceptable solution for a search box.

Yes it is. When the query is more expensive than the entire dataset included in some other query, a static list built from previously queried content is the more performant search, even if you want to classify it as a filter. I, as a user, am still searching through this list of unknown nodes even if you, the program, are just filtering what your nodes are for me. All searches are filters; hard lines for best practices only matter insofar as they engage with their practical application.