Note that the thinness of the cover may not be the only reason Apple only offers a 720p camera on its laptops. Even if it had more space, it might still only offer 720p, as evidenced by the fact that even the latest iMac (2019 design) only has a 720p camera (the 2017 iMac Pro, by contrast, offers 1080p). This tells me that camera quality (as contrasted with, say, display quality) has never been a priority for Apple's Mac line.