Hi Peter,
The benefit of auto-scheduling, is that clients don't need to understand it in order to benefit from it. If a client does a PUT request to create a new event, and that event has an ORGANIZER that matches the current user, and an ATTENDEE that is on the system, sabre/dav will automatically create an item in the inbox for the recipient and a new calendar object on the calendar of the recipient.
Likewise, when that user accepts the invitation by setting PARTSTAT=ACCEPTED, the original organizer's calendar object will also automatically get updated with that information (as well as every other attendee).
So, yes, it does. The inbox is actually not very interesting and is ignored more and more by various calendar client. Most of the information that's in the inbox can actually be inferred from calendar objects that are already on the calendar.
Hope that explains it.
Evert