I can verify that
views-exposed-filter.tpl.php is being loaded for basic JSON endpoints that don't re-render any form fields: My autocomplete - /search_api_autocomplete/search_api_views_flc_biz_search/-/farm - is driven by the View below against Solr, and I'm using project/ajax_facets to POST to
/ajax/ajax_facets/refresh for filtering by other indexed fields.
This breakpoint confirms i'm still loading unnecessary templates during json API calls. I haven't yet dove into the stack trace or scattered more breakpoints to find what is actually loading this, but know that could take many hours to drill down.
For huge performance improvements, how can I avoid all of D7's theming layer when making any requests for JSON?