xDX Designer doesn't support pin direction in the same way as DC, if you turn on Pin Type Arrows it works for all symbols, not just hierarchicsal blocks. We have an internal enhancement request to provide an option to limit Pin Type Arrows to hierarchical blocks only but have not yet decided if or when we will implement such a feature. You could post an Idea on the Ideas site and see if it gains any votes among other xDX Designer users.
I see you logged a new Idea, but having done some searching I found a pre-existing Idea for this and so have closed yours. We cannot merge Ideas currently so you should vote for this Idea instead Display Port Type for Composite symbol only - D15026