This apps also can use internal APIs without faring to be removed from the app store, they can also do UX practices which are not super compatible with the guid

This apps also can use internal APIs without faring to be removed from the app store, they can also do UX practices which are not super compatible with the guid lines and they never need to fear an arbitrary ("accidental") review block/take down. So it's not at all feeding they own dogfood. Do do so Apple would need to run separate finances and make sure they don't get benefited in the review process.