Split Pane not displaying correctly


First note, I’m using @ionic/vue so it could be in that or it could be Ionic on the whole.
Either way, it seems a pretty foundational issue

Using code almost identical to that described here;

Exact code can be read here;

The issue I’m running into is that when the screen size is greater than small, so it splits the screen, the menu is not displaying correctly. And when the screen size is small, so it has a pull out menu, the length of the text in the header determines the width of the header and the entire screen, rather than it filling the length of the screen as one would expect.

Here’s images to better describe what’s going on;