So, essentially this is to enforce the "desired behavior" mentioned above. 

Imagine the reroute map looks like this

1) app-bundle:/// -> file:///android-asset/www/
2) file:///android-asset/www/ -> file:///storage/

Then the flow looks like this.

1) Get a message that we are navigating to a app-bundle: Uri
2) Stop the loading
3) Replace with file:///android-asset/www/whatever
4) Throw the query param "APP_BUNDLE_REPLACED" into that url to get "file:///android-asset/www/whatever?APP_BUNDLE_REPLACED='true' "
5) Now this is where this check comes in. This check says, If we have got to this url by replacing an app-bundle uri, do not do anything.