Exporting a frame is a thing in most NLE's. The catch is you want slow shutter speeds for that natural feel/flow in video, but want higher shutter speeds for that crisp high resolution image.
Your editing process is completely different - it's not like you're exporting CR3's, it's literally grabbing a frame hopefully you've color graded & exporting it as a jpeg. So the image quality is highly variable & may not be suitable for large prints compared to the normal 45mp shot.