React Native - Global BackHandler behavior depends on registration timing - react-native

Question

I'm migrating an old React Native app from 0.57 to 0.62, and just setup navigation with the current React Navigation package. That app contains a global navigation store that registers to Android back button presses and allows me to intercept back operations, no matter where they originate (hardware button or programmatically).
I have a rather weird behavior here, and it seems to be timing-related. In the snippet below, I register a listener with BackHandler, which supresses back button taps and logs a warning. I'll register it in the componentDidMount method.
export class RootComponent extends React.Component {
private initBackButton() {
const onBackPress = () => {
console.warn("BACK BUTTON SUPPRESSED");
return true;
};
BackHandler.addEventListener("hardwareBackPress", onBackPress);
}
public componentDidMount() {
// TODO register back listener
}
public render() {
return (
<NavigationContainer >
<StackNavigatorSetup />
</NavigationContainer>
);
}
}
If I register the listener synchronously, the back button listener fires if I press it at the initial screen of my StackNavigator.
If I navigate to a second screen, the listener does not fire if I press the back button, and I can return back to the start screen. If I press back there again, the listener fires.
Note that I'm declaring the listener in the root component, so that component isn't going anywhere.
public componentDidMount() {
// only works on the start screen
this.initBackButton();
}
Now, the behavior is different if I use a delay:
If I register the same handler with a delay of 1 second, the handler works on any screen
This is not thread-related. If I use a delay that is too short, it again only works on the start screen
public componentDidMount() {
// works on every screen i'll navigate to
PromiseUtil.delay(1000).then(() => this.initBackButton());
}
To be honest, I don't really have a clue what's happening here. BackHandler seems to be ready, but I don't understand why the listener works either global or not depending on the delay. Also, my root component doesn't really change, so I wonder whether React Navigation is messing with me here...