None of any of that applies to the point at which he was writing the test, and all of it would be covered by the integration tests he says he writes.

I have seen some truly awful, pointless, tightly-coupled controller tests (testing if an instance variable is assigned, for example) in my career. If there's enough logic in a controller that testing it at a level lower than a general acceptance/integration test is useful, it should almost certainly be in a model or a service object.