Make Modern Search API Available
We are finding many difficulties where custom code needs to roll up search results in a similar way to the OOTB modern search experience.
Unfortunately it appears impossible to return the same results/order via /api/search/query through traditional means than that of the Modern Search Results page. Upon investigation this is due to a special request property which appears to be around personalization (DynamicContextLists, which is sent as part of the search request when on a OOTB Modern Search Page such as /layouts/15/search.aspx)
Without this we cannot provide a proper flow from a custom search webpart/extension, into the OOTB search results. This is often needed for scenarios where the user wants to 'See More' results or we want the user to be redirected to a familiar interface as well as for further refinement ability.