willEnterForegroundNotification not get called on app launch

class AppDelegate: NSObject, UIApplicationDelegate, UISplitViewControllerDelegate {
    var window: UIWindow?
    @objc
    func pendoEnterForeground() {
        print("pendoEnterForeground")
    }
    func applicationWillEnterForeground(_ application: UIApplication) {
        print("applicationWillEnterForeground")
    }


    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        NotificationCenter.default.addObserver(self, selector: #selector(pendoEnterForeground), name: UIApplication.willEnterForegroundNotification, object: nil)
       ...

Th following works correctly on app with scenes BUT on old apps without scenes the following doesn't work on App launch (on the following foreground background it does work)i.e:pendoEnterForeground and applicationWillEnterForeground doesn't get triggered on first app launch.