When you tap to see the full closure reason for an off-topic question (e.g. this one) on the Android App (version 1.0.38), you see something like this:
This question does not appear to be about on-topic within the scope defined in the help center.
This was an issue with our API handling old questions that were closed using the default off-topic reason. It's been updated in the backend and is fixed in the app right now. Thanks!