playkia I'd also guess that the iOS version is responsible for the problem, yes!
In Xcode projects, you can configure a "deployment target", which defines the iOS version that's required for an app to run. My expectation is that this mostly influences the compilation of the actual binary (by telling the compiler which dependencies it can count on). But who knows – in case Apple changed the way the launch screen storyboard works, Xcode might also create a different version of that file, depending on the target. It's just an experiment – but maybe worth a try! So, please check the deployment target in the Xcode project you're using to create the storyboard:
→ In the "General" tab of your project (click on the project name in the navigator on the left) set “Deployment Target” to a value that includes both your test devices. Then export the storyboard, and maybe Assets.car, again – perhaps this makes a difference.