Well not hidden exactly, but subtle. A while ago I requested we add this capability to the WCSF Guidance package, and then I forgot about it. Well today I was playing around with the new GP and to my surprise saw the following.
Yes, you can now create an interface project for a module. This is very useful if your module is exposing services which need to be accessed by other modules, and you don't want them having any hard references to the project which holds the implementation. Which by the way is a good enforcement of the SRP principle.
As a side note, today Lana and I are having our five year anniversary. I guess this is my team's anniversary gift? :)