Notifications in the app alert you about new episodes for shows you haven’t started watching.
For example, you get notified about a new episode from a show that is already in its 4th season, but you haven’t watched a single episode.
“New episode” notifications should be for shows that are either premiering their first episode or shows for which the user has watched at least one episode, meaning they are actively watching that series. Otherwise, it doesn’t make much sense to be notified about a show in your watchlist that you haven’t started yet, like getting an alert for a new episode from season 4, for example.