Regarding Event Updates Using GraphAPI

Question

I am developing a system that copies resource reservations to another service using the GraphAPI. However, I've encountered an issue where guests (email addresses without associated users) are not being added to the resource events.

The issue occurs as follows:

1. Create an event in Office365 specifying a meeting room.
2. Retrieve the reservation using GraphAPI: /users/{ResourceId}/events/{EventID}.
3. In Office365, add a guest (an email address without a user) as an attendee to the reservation created in step 1.
4. Retrieve the reservation again using GraphAPI: /users/{ResourceId}/events/{EventID}.
5. Upon reviewing the event retrieved in step 4, the guest (email address without a user) is not included.

It's worth noting that when retrieving the reservation with /users/{UserId}/events/{EventID}, the guest (email address without a user) is included in the event.

I would like to inquire about the possible reasons why guests (email addresses without users) are not included in events retrieved with /users/{ResourceId}/events/{EventID}.

I appreciate your assistance in this matter.