This is a great article. I follow the author on dribble and have always liked his animations. Glad to see he shared his thoughts with the design community.
All of these prototyping tools are great, but don't forget just paper prototyping. We've been doing a lot of AR paper prototyping (so lots of things on strings and hanging from the ceiling), and it's a pretty fun experience that really let's us define interactions.
That was a neat idea!