Swift UIApplication.shared.open from backgrounded app not working

Question

I'm trying to send a message to an app (appA) from another app that is in the background (appB).

Seems like from he Apple docs (https://developer.apple.com/library/content/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html) that it's possible.

What I am seeing, however, is that I can launch appA from appB when appB is in the foreground.

When appB is in the background the methods fire (I see the print statements in Xcode) but they are not received in the

application(_ app: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any] = [:]) -> Bool

function in the app delegate of appA

Is this behavior not allowed?

I have even added the background modes for appB in the plist.

class ViewController: UIViewController {
let kUrlSceme = "customScheme://?hello"
@IBOutlet weak var logTxtView: UITextView!
var runningLog: String = ""
var executionTimer: Timer!
var backgroundTask: UIBackgroundTaskIdentifier = UIBackgroundTaskInvalid

override func viewDidLoad() {
    super.viewDidLoad()

    self.openOtherApp()

    executionTimer = Timer.scheduledTimer(timeInterval: 5.0, target: self, selector: #selector(self.openOtherAppFromTimer), userInfo: nil, repeats: true)
    registerBackgroundTask()
}

func registerBackgroundTask() {
    let str: String = "Background task started."
    print(str)
    runningLog.append(str)
    logTxtView.text = runningLog

    backgroundTask = UIApplication.shared.beginBackgroundTask(expirationHandler: {
        [unowned self] in
        self.endBackgroundTask()
    })

    assert(backgroundTask != UIBackgroundTaskInvalid)
}

func endBackgroundTask() {
    let str: String = "Background task ended."
    print(str)
    runningLog.append(str)
    logTxtView.text = runningLog

    //        UIApplication.shared.endBackgroundTask(backgroundTask)
    //        backgroundTask = UIBackgroundTaskInvalid
}

@objc func openOtherAppFromTimer() {
    //        executionTimer.invalidate()

    var str: String = "Attempting to call fromt he timer."
    runningLog.append(str)
    logTxtView.text = runningLog
    //
    //        self.openOtherApp()

    let theURLSceme = URL(string: kUrlSceme)!

    if UIApplication.shared.canOpenURL(theURLSceme) {
        UIApplication.shared.open(theURLSceme)

        str = "We have permission to open the URL (\(kUrlSceme)).\n"
        print(str)
        runningLog.append(str)
        logTxtView.text = runningLog
    } else {
        str = "Looks like we don't have permission to open \(kUrlSceme).\n"
        print(str)
        runningLog.append(str)
        logTxtView.text = str
    }
}

func openOtherApp() {
    var str: String = ""

    if openDeepLinkScheme(customURLScheme: kUrlSceme) {
        str = "app was opened with the URL: \(kUrlSceme)\n\n"
        print(str)
        runningLog.append(str)
        logTxtView.text = runningLog
    } else {
        str = "app was not opened\n"
        print(str)
        runningLog.append(str)
        logTxtView.text = runningLog
    }
}

func openDeepLinkScheme(customURLScheme: String) -> Bool {
    let theURLSceme = URL(string: customURLScheme)!
    var str: String = ""

    if UIApplication.shared.canOpenURL(theURLSceme) {
        UIApplication.shared.open(theURLSceme)

        str = "We have permission to open the URL (\(kUrlSceme)).\n"
        print(str)
        runningLog.append(str)
        logTxtView.text = runningLog

        return true
    }

    str = "Looks like we don't have permission to open \(kUrlSceme).\n"
    print(str)
    runningLog.append(str)
    logTxtView.text = str

    return false
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


}

Thanks for the help.