Overall good read. The author didn't touch on this, but it's incredibly important to consider gestures when creating animations. If a screen slides in, it indicates that you can swipe it in the reverse direction to get rid of it. If a modal scales up, it indicates that you can swipe it down to dismiss it (similar to photos in ios9).
This applies to all UI animations IMO. It can be frustrating to set expectations through an animation and not follow through with the proper gesture integrations.
YES! Totally agree, gestures and interaction are incredibly important for making an interface behave in a semantic, predictable way. We didn't want to pack too much into one article, but we are very interested in that aspect of semantic animation, especially since there are a lot of bad examples of this out there (hello cards that rotate when I simply swipe them horizontally). It's great to hear that you are thinking along the same lines.