The spec only states that:
This does NOT mean that other port types can't be typed by an InterfaceBlock!
If it is stated that 'all fish live in the water' does it mean that dolphins (which are mammals) do not live in the water?
In particular, one might wish to type a "standard" Port by an InterfaceBlock or a conjugating ~InterfaceBlock.
And why might one want to type a "standard" Port by an InterfaceBlock?
Reason 1: As part of an incremental development process (before committing to using a ProxyPort or FullPort (in which case one might wish to first extend the InterfaceBlock)
Please see also under: