Confused about the new Focus app

There is one thing that is not clear to me. When setting up a focus profile, you can configure what will get through to notifications in two ways :Allow People and Allowed apps. But how these interact is not clear to me! Let us say I want to be notified if I get an SMS from "Joe Bloggs". This will come via the "Messages" app. Do I have to BOTH add him to "Allowed People" AND also add Messages to "Allowed apps"? Or do EITHER one of these is all that is needed for his messages to be notified?

This is not clear to me.