Multiple Selection List filter is styled or templated wrong in Shiny theme when not in Commerce Kickstart

I recently started using the Shiny theme for administration (and love it, by the way), and noticed that it has a new version of the multiple selection list filter:

It isn't just a pop-up menu that lets you only choose one filter term, or a scrolling list that lets you click on multiple terms by which to filter… Instead it looks as compact and clean as a pop-up menu, but when you click on it, it lets you add multiple terms to the filter. It's elegant and fast and the best ui innovation I've seen on Drupal in a while.

However, I only see it in my stock install of Commerce Kickstart (which I have installed on my laptop using Acquia Dev Desktop -- just to see a model of Kickstart). In that environment, Shiny shows the selection filter that way.

However, using the same Shiny theme on my live site, which has Commerce and Commerce Backoffice installed, the selection list looks different -- perhaps broken. It just shows a medium length scrolling list, but with no scroll arrows. It's difficult to use, ugly, and mistake prone. I would really like the correct version I've seen in Kickstart.

Screenshots are attached.

I really the response could be, "it's your environment's problem, since it works on Kickstart". However, I'd like to find out what is the causative factor; and try to figure out what goes wrong between the controlled and relatively closed Kickstart environment and my live, open site.

Does anyone know what might be causing the difference? Is there another module or library I need to install to make this work? Is there another known bug related to this issue (I can't even figure out a way to search for issues related to this.)