Not every change is going to completely overhaul the app. More than likely, the changes are a fix to some obscure bug not caught in testing that only affects a small percentage of devices. Just because you don’t encounter it with your workflow and device doesn’t mean it isn’t a critical bug preventing someone from using the app. It could also be a new feature targeting a different use case to yours. It could even be as simple as bringing the app into compliance with new platform requirements or government regulations (which can happen a couple times a year, for example Android often bumps the minimum SDK target such that apps are forced to comply with new privacy improvements).
You definitely need approval to publish on the Play Store. It’s just more basic