Universal search does not get an exact match for a place display_name

[kueda]

E.g. https://api.inaturalist.org/v1/search?q=Washington+County%2C+US%2C+OK returns no results even though the display_name of https://www.inaturalist.org/places/washington-county-ok-us is Washington County, US, OK.

https://github.com/inaturalist/iNaturalistAPI/blob/main/lib/controllers/v1/search_controller.js#L69 suggests we are matching against all fields ending in _autocomplete, and the places index has a display_name_autocomplete field, so why isn't this working?