Whether you search directly on the Facebook search box or using the Graph, the search result page are from Facebook.
Not the Graph.
Facebook is responsible for anything that appears on the search result page.
The Graph only helps the process of constructing the keywords on the Facebook searching procedures.
The results are 100% from Facebook.
Some Factors That Affect Graph Search Results
By default, Facebook priorities the results that are derived from closest people around the Facebook users who are searching.
Therefore, the search results of one Facebook account will be different from other accounts.
The location where the Facebook users do the search also affects the results.
Facebook will show some results which locations are around the Facebook account that you use to search.
On Facebook we can control who can see our status updates, birthday date, email, phone numbers, etc.
That will definitely affect the search results.
Most of the search results are taken from the items that the privacy setting is set for public.