How to resume audio playing of other apps after dismissing AVPlayerViewController?

I use AVPlayerViewController to play short videos in my app.

If there is an app playing audio in background before user plays a video in my app, I want the background audio playing of the other app to resume after my video player is dismissed. I currently use AVAudioSession.setActive(false, with: .notifyOthersOnDeactivation) to do that.

Even though Apple's Music app and Podcasts app do resume playing after I call AVAudioSession.setActive(false, with: .notifyOthersOnDeactivation)—won't resume without the call so it means this call does have effect—none of the 3rd party music or podcast apps that I tested(Spotify, SoundCloud, Amazon Music, Overcast) do.

I doubt it's because none of these popular 3rd party apps supports background audio resuming. There must be something missing in my code:

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        // I know it's not the best place to call setActive nor it covers all the cases. It's just a convenient place to put the code to test its effect after dismissing the video player.
        do {
            try AVAudioSession.sharedInstance().setActive(false, with: .notifyOthersOnDeactivation)
            try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryAmbient)
            try AVAudioSession.sharedInstance().setActive(true)
        } catch {
            print(error)
        }
    }

    @IBAction func play(_ sender: Any) {
        do {
            try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
            try AVAudioSession.sharedInstance().setActive(true)
        } catch {
            print(error)
        }

        let playerController = AVPlayerViewController()
        playerController.player = AVPlayer(url: URL(string: "http://gslb.miaopai.com/stream/UkjiD45ddxZFQ79I2bLaGg__.mp4")!)
        playerController.player?.play()
        present(playerController, animated: true)
    }

}

Even though someone on Stack Overflow thinks this code is fine and its these 3rd party apps' fault, I still believe there are something that can be done to make them resume audio playback because Twitter app can. But I don't know what Twitter does to achieve that, anyone knows?

PS: here is the complete project so anyone interested can try it.