As we said, the themes which you can get a notification on the top area like your screenshot are all in wordpress.org.
To be extactly, those themes are all free themes which can be downloaded on wordpress org.
In wordpress dashboard, the appearnace theme page is connected with wordpress org server.
So wordpress org themes can be shown the update notification like your screenshot.
But envato themes are not on wordpress org. So you can't see the screenshot notification from themeforest themes such as avada, flatsome...
To be exactly, the top area notification comes from wordpress org, not themeforest marketplace.
And as you said, same happens for themes that come from the themeforest market place.
Some themeforest themes are uploaded on wordpress org, but those are all free version, not premium.
They removed some important features and made free version. Then, upload it on wordpress org.
If so, you can get the notification for the free version theme, but you can't get the notification for the premium version.
As we said, you can get the updated notification from envato marketplace.
If you create your account correctly on themeforest, you can get the updated notification from your account email like screenshot.
All envato marketplace items such as themeforest, codecanyon are sending their update notification like this.
I hope you can understand this problem correctly. If we update theme, we also send the email notification to our buyers.
If you have any questions, please let us know again without hesitation.
Best Regards, C-Themes