The Google Authenticator app was used to store one time password on only the primary device. This meant that if you lost access to your device, you would not be able to access any of your accounts secured with the 2FA mechanism. Now, the Account Synchronization feature for Google Authenticator lets you backup your 2FA codes to the cloud which allows you to access the code from other devices.
While this feature is a convenient option, it can leave you vulnerable to risks. Anyone who has access to your Google Account device may easily access any 2FA code synched to it and gain access to all associated accounts.
How to disable Google Authenticator sync feature?
You can disable this feature by following these steps:
On your device, open the Google Authenticator app.