It's init + your app, which is exactly what you want. PID 1 has some important responsibilities that aren't handled anywhere else. I'd argue that most init systems go far beyond what you actually want PID 1 to do, but that is a different discussion.
I definitely don't want any init in the container. I want the app runnning in there and nothing else. For a single application system, pid 1 has only 1 responsibility - collect zombies. I treat that as an emergency solution - apps should clean their children themselves under normal circumstances.
Everything else can be handled outside of the container.
