Hi Robin,
As I understand it, the app is just a wrapper for the WebUI, that makes it so that you don't have to open your browser manually and type in the IP address to get to the WebUI. (If that's wrong, somebody please correct me.) If you're okay to open the browser yourself, there's a setting that allows you to pick the style you want. I'd expect that setting to work with the app, but apparently, the app is overriding it somehow.
Also, I've heard that people have been able to hack together something that will open the browser to a specific page. Maybe somebody can post and tell us how.