I realised this first when debugging my app on the ios13 for the first time BUT it behaves the same way for 10, 11 and 12, just doesn't work the same way with debugger.
I can't find anything about this "bug" in the documents. I want it to behave the same way as on Android i.e. OnSleep freeze everything on the App.
Some guidence on the subject. The App has a lot for timers running.