The better question is what counts as social media? Is HN social media that under 16yo Australians need to be kept away from?
So I guess it's aimed at sites that are supposed to cause these problems?
We can extend that thought further than just HN. The reporter (surprisingly!) brings up something we've known for a while but has been slow getting traction. That the relation between noted harms and SM is far from clear.
There really is not a super clear causal link between greater use of social media and upticks in anxiety and depression among teens.
Regarding youth mental health, there are strong causal competitors (to SM) that aren't well examined. Like the elimination of free roaming areas (from sq mi to sq ft), attacks on child independence (false stranger danger messaging) and car culture + trespassing culture (traded endless walkable areas for narrow death zones).
I argue that since mid-1900s, we've eradicated most of what kids needed to learn complex problem solving, develop ambition and earn self-esteem.
If I wanted to erode youth mental health, I'd do exactly what we've done. I'd get rid of irreplaceable environments where youth experienced critical growth.