Calendar and Contact Integration - does it sync both ways?

I recently migrated a client from Google to M365. Some users have personal Zoom accounts. They were syncing the Zoom calendar to the Google calendar.

Now that they're on M365 using Outlook Web and have permitted the Zoom integration app to access their accounts, the existing meetings in the Zoom calendar are not appearing in the M365 calendar. Only new meetings created with the Zoom Add-In are appearing in both calendars. Is this normal behavior? 

Thanks!