I'm encountering the same error message with an app intents extension. As a workaround, I've disabled the extension and added its code to my main app target. I'm not sure if this is also possible in your case.

I have received the following feedback from Apple: This is correct behaviour. If you have both a phone and watch app installed we’ll try to coordinate between phone and watch notifications if the phone is unlocked. If the app developer doesn’t send a notification on the phone the watch will timeout after 13 seconds and alert anyway. The best solution to this would be to send the same notification on both devices ensuring the UNNotificationRequest.identifier matches on a per-instance basis. This will let us alert and deduce correctly.

I'm experiencing the same issue since watchOS 8.0. I've submitted a bug report: FB9842030