Updates get "tested", but unless it just immediately crashes on launch, this is not a reason for rejection.
Screenshot updates are not necessary (just recommend to improve your rankings), and eventually answering some questions like "do you handle personal information in the app?". There's a few edge cases where you need to prove that you're using a specific permission for good reason.
So it‘s not just a simple rebuild and an upload but Google wants certain screenshots of the app and all kinds of additional information