Mine: require setting a URL to support password managers. You download an app, go to login, tap the password field, and open Bitwarden. Does it find your login? Half the time, nope! The dev didn’t tell Apple one time what their URL is, so everyone now has to search their password manager every time.
I know 1Password can detect the app ID and use that as a match criteria. The problem is that it is not user intuitive to get the app ID to key into password manager; also doesn’t change the fact that the app most of the time just front end to some website, which already has an entry for the website, and shouldn’t require the user to go out of their way to find App ID to work around the dev’s inability to surfacing basic metadata about their service.