Group members automatically added to events for SOME of our Groups

Group members automatically added to events for SOME of our Groups

Why is it that when we enter events on our Group calendars, in some cases all members of the Group are automatically added as invited attendees and for other Groups, NONE of the members are added automatically. I can't find any settings to explain this. The Group calendars I am referring to are from Groups that I created in the cPanel for Zoho (as our Super Admin). I am not referring to individual groups our users may have created. Please advise.