Well, that explains things 🙂

I don’t think Jerboa supports ‘native notifications’ which means it relies on other services (such as Google Play Services) in order to push notifications to your phone. Some applications (such as Fairmail, F-Droid) don’t rely on Google’s services and use the OS’s native notification abilities.

If you’re looking for faster updates, you might want to give Obtainium a try. I’ve been using it and it works great.