To launch the splashscreen, I use the images.xcassets with the LaunchImages. The problem is that it works perfeclty with the simulator, but not with an iPad (iPad 4th generation, ios 10.1).
Where do you think the problem comes from?
I just tried this myself in the simulator. I forgot to delete the "Launch Screen File" after setting the "Launch Images Source". This resulted in the LaunchScreen.storyboard being used every time, even after I deleted the setting! Deleting the app and re-deploying solved the problem.
Is it possible the same is happening on your device? Try deleting the app from your device and re-deploying.