I don't know about you, but I have done it many, many times, and I have never encountered a client who doesn't want to tweak and add and tweak and sometimes reject, then conditionally approve, their way to deployment.
The difference is that Apple can veto the very concept of the app, after the fact. E.g.: google voice clients, podcast receivers, etc. (the list of examples is quite long). There's a difference between requiring a late tweak and vetoing the core functionality of the app.