It seems like if you were co-executing the client on the server you could trivially achieve perfect fetching. GraphQL may actually over fetch in many situations. Here's an example: the client fetches a list of objects, filters it, and then fetches more data referenced by the results. With GraphQL, if you don't automagically parse the filter out of the client code, you over-fetch. However, the HTTP/2 solution could just push the 2nd fetch as it was made by the co-executed client.
All that being said, GraphQL certainly alleviates the server-side load co-execution would imply and that's likely more suitable to the scale Facebook operates at.
