I've never heard, or seen that before. Everything I've ever seen rejected by Apple (either personally from my own apps, clients, or from press reports) has always been a guideline issue.

So, "Subjective reasons" such as? Example?

Here is an example of a 3D game running on the Apple Watch, that was approved by Apple, on the App Store, which looks rather "Quake like". Mindkeeper: The lurking fear (Apple Watch)[https://apps.apple.com/us/app/mindkeeper-the-lurking-fear/id...]