When you say "MQ->MQ routing (federation)" I have a hard time understanding how that is not close to leaf nodes. Leaf nodes allow independently operated / manag

When you say "MQ->MQ routing (federation)" I have a hard time understanding how that is not close to leaf nodes. Leaf nodes allow independently operated / managed NATS servers to share data back and forth, which to me is what federation is about. Do you have any resources you recommend to help me grasp why this is different?