From experience doing mobile development at work, natively for both Android and iOS, Apple does test and run your app to make sure it works and that it does what it promises to do. I can see it because we issue both Google and Apple accounts and I can see when they get used. While Apple's app review is harsh, it did make our app higher quality and they are quick to reject when there are bugs. They run our app on every review and go through their checklist. Apple is also quick to question the permissions we ask for and make us justify them. In one instance, whoever did the app review, listened to our justification and actually recommended a better, alternative approach. Android, Google test ran our app when we put it up for the first review and havn't used their test credentials for any subsequent reviews to push app updates. We totally could just completely bust our app, push it to the store or do whatever we want and there seems like little to no oversight.