Hey!
Good news this is something you can fix really easily for your project.
This is related to the project not utilising the new "Image.assets" and the new "LaunchScreen"
The openFrameworks Core is tracking this issue with a solution for the Template Project here:
So for iPad Pro support... In Xcode ... Add a new "LaunchScreen Storyboard".
This will also give you fullscreen / full rez iPhone6 + (you will also need to migrate the icons to a Image.assets).