As Per checking, the Drill Down Fields are specifically set for viewing Saved Search results externally. Under the Results tab > Drill Down subtab, you can also see a note that says “Select fields you would like displayed when a customer viewing search results on your Web or intranet site drills down to the record.”
There is also an Enhancement 167665 Lists > Search> Saved Searches> New> Transaction> Results Tab>Drill down Fields sub Tab: Ability to use the drill down fields to display fields on the search results within Netsuite UI without using Intranet related to this.