In both the latest iOS beta (v1.4.20) and at least the previous released version, the "Service Screen" setting does not survive across restarts of the app.
Steps to reproduce:
* Open app, go to settings
* Toggle on Service Screen
* Tap Done
* Force quit the app
* Reopen app and notice only 4 screens, go to settings to confirm.
It doesn't seem to matter how long you use the app for or whether you force quit it or if iOS shuts it down after some inactivity, the setting is never persisted.