My own experience indicates the apple-app-site-association file is checked when the app is first installed, and then rechecked during any later app updates from the App Store. So if you add an additional path to the file, it would be detected when the next update app is released but likely not before.
Note: if you’re testing locally, you need to completely delete the app before reinstalling. Except for App Store updates, it appears the apple-app-site-association is not rechecked if the app is already on your device.