You are right, but you are missing the frontend part.

e.g. frontend says "backend, give me the users". Then later, for every user it says "backend, given me the users favourite images". However, with graphql the frontend can say "backend, give me the users and include each favourites images".

Even if the way to retrieve it from the database is the same for the backend, there is still reduced latency because it is only

frontend->backend->db (users)->backend->db (images)->backend->frontend

instead of

frontend->backend->db (users)->backend->frontend->backend->db (images)->backend->frontend