I did some more research on this.
I believe that the schema part is something we should support. However the type Query with an empty body violates the GraphQL schema. Here is the reference. Specifically the first point
An Object type must define one or more fields.
We can try to resolve this with a transformation on the SDL API request. Let me know if you are interested I can wait for you on that.
I am wondering if we can build an SDL transformer for java-graphql because the routing and query building works fine. Its just the SDL format.