Most of the apps caught in the review process are probably those that fail other guidelines (usefulness, privacy concerns, illegal/inappropriate content, poor UX/quality, excessive crashing, etc). Most of those things can't be caught by automated means, and the content-related things can certainly be changed after initial review.
I've personally worked on several apps that significantly modify app behavior after being published - not so much to bypass any review requirements, but rather to adapt to changing business needs without waiting to publish a new release.