> the outermost pointer can still be null, so you are still vulnerable to a NullPointerException

This is true, but there is a distinction: if your Optional value is null, for any reason, then it's a programming error and should be fixed. If a non-Optional value is null, there's no telling whether it's "allowed" to be null or not. So I never null-check my Optionals in Java -- I'd rather they fail so I can be alerted to them.