You can try this URL: https://www.triumdesigns.com/media/default.mp4
I guess when the browser plays a video, it might be using the internal video player of the corresponding platform and this internal video player does not get closed on browser close. I can say this from the video player UI on iOS. The player keeps on playing the video in the background when I close the InAppBrowser while the video is playing. You will still be able to hear the sound of the video after closing the browser. If I pause the video and then close the browser, it works normally.
Let me know if I can somehow work around this.