Having seen this from the inside, well known platforms get more forgiving treatment from app reviewers even if policies are nominally the same for all apps. If Tumblr launches a new or heavily redesigned app and they have adult content, the review process may block it even if Reddit's app has similarly graphic content.
Oh, I know. But they are correct that the policies state that this is the case, even though Tumblr does still have quite a bit of porn, both compliant and not.
