Ah, so it goes the other way too. Sort of like a request inliner/outliner that can perform dynamic optimizations. The client can inline requests using view-state unknown to the server. Then the server can outline them in whatever desirable way to provide an immediate and eventually complete response. That's clever.
GraphQL endpoints don't have to return a single JSON object either, you could hypothetically stream back objects as they become available (Netflix's Falcor seems to be heading in this direction too).