I just contacted APPLE DEVELOPER via phone from Singapore at 1:43 PM SG time zone.
The advisor on the line confirmed:
If you have this problem, create a new release version
you do not have to upload a new binary
you do not have to submit this new release for formal review
just navigate on the left menu to General > App Information.. go update your age ratings
once done the section will show Edited
That's all. You have done your part
To know if you have any pending actions, go to appstore connect website on browser
Https://appstoreconnect.apple.com
If there are no banners or alerts on the main page, you have nothing to worry about.
TLDR:
just add a new version so that you can edit your age ratings; but there is no need to submit it for full app review and there is no need to upload a new binary.
if there is no banner or policy flag on your appstoreconnect account you dont need to worry or do anything