I think this is a little less sinister than you are making it out to be. To me, it reads as the intent of those exemptions is because those sites (CNN, Fox, ESPN, etc) exercise editorial discretion around what content is posted and, presumably, should be more active in moderating/enabling/disabling discussion comments. Sites like reddit (since you mention r/exmormon) while are user moderated ultimately escape liability behind section 230.

It's a separate debate for us to argue what is more harmful to children/minors/teens - news/sports/entertainment media vs social media but with our current legal framework these exemptions kinda make sense. If what you are worried about is brainwashing, being solicited, general harm from both users and algorithms, its probably true that that is less likely to happen to a kid in the comments section of an ESPN article than it is on reddit/4chan/tiktok/instagram - and when it does happen at least there is someone to hold somewhat responsible.