Adobe Campaign(AC) interacts with both author & publish. Example delivery of newsletter after all the approval phase will interact with publish.
For unapproved Email template AC interacts with author & is required in AC side so that campaign approval managers can use it for budget/target/planning approvals. Note still template is not possible to edit in AC since it is not approved. So unapproved template uses author where once approved will use publish instance. The main advantage of providing unapproved template available in AC is so that markers & content creator work independently & to know each other work. So that time is reduced for overall deliver-ability.