I have set up and uploaded an app to the closed testing track in the Play Store Console, where it was reviewed for three days and approved.
Now, I just wanted to run a small update/patch for the app and uploaded a new app bundle for this. This new version is now again in review by in the Console.
Will this always be the case? Are these reviews of updates maybe faster than for the initial version?
Just to sum up my own experience here: As alright indicated by the helpful comments above, all further updates/releases within the closed testing track (and also open testing and production) need to be individually reviewed and approved as well by Google Console.
However, my updates were mostly approved within one hour or two, much faster than the initial release in the closed testing track.
Updates in production mostly got reviewed within a day.