There is a Web Viewer, but that's not yet fully functional. I believe that is coming shortly after the official release date.
What you are seeing of Quicktime, is actually being Previewed on an iPad, connected to a computer, and is being mirrored on the screen through a "New Movie Recording". This is a little trick that is done to: screen record an ipad, share an iPad through a web meeting, or simply display the iPad on the desktop.
So, in short, to your question, you can't really preview DPS 2015 through QuickTime, you can merely mirror the iPad or connected device through QuickTime.
You can (or will be able to) preview on the desktop through the built in Web Viewer (which is still in development).