It obviously has something to do with the underlying "cordova plugin add" process that is being performed under the hood to add plugins to your project. Whether or not the situation described in the link above is comparable to yours would be good to know. The solution I provided there is not yet proven to be correct, as I was only able to partially reproduce the issue.
I am unable to reproduce the issue using the project you provided. I'm also using a Mac with same version of Sierra. The only thing I can think of is to try clearing the local XDK cache. Use the process outlined in the fourth bullet in this FAQ > https://software.intel.com/en-us/xdk/faqs/general#recover-xdk < and be sure to make a copy of the global-settings.xdk file first, then put it back after you've deleted everything, but before you re-open the XDK.
Here's a link to do a complete uninstall (on a Mac it's pretty easy) > https://software.intel.com/en-us/xdk/faqs/general#uninstall-xdk < note that the latest version adds an extra folder during install, which is not described in that FAQ. If you find the old copy still in your /Applications folder, then remove that one, as well.
