You have control over what queries/entities get exposed in the graph. I think what he's saying is that most nested entities can be mapped to simple 'SELECT .. f

You have control over what queries/entities get exposed in the graph. I think what he's saying is that most nested entities can be mapped to simple 'SELECT .. from .. where id = 1,2,3' queries, and a while a well-written JOIN might be more efficient, those have known performance and can benefit from caching, sharding etc.