The problem there is you can't have a single URL that just goes to the web page if there's no app installed. That's what the author is trying to solve.
Android has a solution where an app can handle all links to a certain domain. (The OS asks you if you want to use the browser or the app, and you can set it to always use the app if you like.)
I think from an HTTP perspective, the right way to solve this is to use vendor specific content types and have the OS resolve whether to open it in an app or not.
So when a link is clicked on in a browser, you use the request's Accept header to indicate which apps are installed on the device (and have registered a custom content-type). The server then can respond with a custom content type and let the OS dispatch the response to the appropriate app.
For app to app links, the OS could just perform an HTTP HEAD to see which app to dispatch to.
Last I recall, this is how YouTube works to open the app when you try to play it from the web player on a mobile device.