Adding event creates a meeting, not an event instance

I'm using the Microsoft Graph JavaScript Client Library to add events to other user's calendars but they are being added as meetings. How do I ensure they are added as events?
The payload looks like this:
const event = { location: { displayName: 'Office' }, subject: 'Test', body: { contentType: 'Text', content: 'Test' }, start: { dateTime: '2023-03-17T15:00:00', timeZone: 'GMT Standard Time' }, end: { dateTime: '2023-03-17T16:00:00', timeZone: 'GMT Standard Time' } };
And the call to the graph client:
async addCalendarEvent(event) { await this.client .api('/users/someone@somewhere.com/calendar/events') .post(event); }
Hi @SaranyaMadhu-MSFT
Thank you for looking at this.
That is my entire payload.
I can confirm that the response property isOnlineMeeting is false.
When I hover over the 'event' in Outlook it shows as a meeting.