If not, what does it mean?
It means the Garmin Connect Mobile app is thus allowed to send iOS calendar entries to a paired and connected Garmin device for the purposes of generating notifications/reminders and populating the Calendar widget (if there is one on the device).
It does not mean there is any integration between a user's calendar in Garmin Connect (containing activity entries and planned workouts, etc.) and the iOS calendar, so that the user could just look at one or the other and see everything.
So, are you saying that iOS calendar notifications will appear via the Calendar widget on the watch even though they're not appearing in the GCM app on the phone?