Flutter App + Google Calendar API : events.insert not returning 'conferenceData'

I am following this github code as an example to create a google calendar event in a workspace calendar using a service account.

I followed various examples on how to authenticate and connect using a service account and now I am able to create an event and it shows up in the workspace calendar as well successfully.

However, the event that is returned does not have the 'conferenceData' from which I could fetch the 'conferenceId' to create the google meet link.

Below is the insert code that I use, which works but does not return the said conference data.

       await calendar.events.insert(event, calendarId,
              conferenceDataVersion: 1, sendUpdates: "none")
          .then((value) {
            print("Event Status: ${value.status}");
            if (value.status == "confirmed") {
              print(value.toJson().toString());
              String joiningLink;
              String eventId;

              eventId = value.id; 
              joiningLink = "https://meet.google.com/${value.conferenceData?.conferenceId}";
            
              print('Event added to Google Calendar : $joiningLink');
            }
           }
          });

Here's the output I get printed to the console:

I/flutter ( 2934): Event Status: confirmed
I/flutter ( 2934): {created: 2022-07-26T16:12:20.000Z, creator: Instance of 'EventCreator', description: xxxx-desc, end: Instance of 'EventDateTime', etag: "3317703881666000", eventType: default, htmlLink: https://www.google.com/calendar/event?eid=djc1b2gyY3RzZ2p1YWGo4aWtmdWIydG5pZ3R2aGNvNEBn, iCalUID: v75oh2ctsgjuahtircv@google.com, id: v75oh2ctv7itndnc, kind: calendar#event, location: Google Meet, organizer: Instance of 'EventOrganizer', reminders: Instance of 'EventReminders', sequence: 0, start: Instance of 'EventDateTime', status: confirmed, summary: xxxxxxx, updated: 2022-07-26T16:12:20.833Z}
I/flutter ( 2934): Event added to Google Calendar : https://meet.google.com/null

Any suggestions on how to get the conferenceData and hence the conferenceId?

*** EDIT ****

Something else turned up while I was digging around:

While it doesn't matter for my use case, but google api won't allow me to add attendees - even if it is the service account email id.

Error creating event DetailedApiRequestError(status: 403, message: Service accounts cannot invite attendees without Domain-Wide Delegation of Authority.)

I don't understand, domain-wide delegation is already done for this account and that is why I am able to authenticate and create a calendar event in the first place.

Is my understanding wrong?