> I think it’s a mistake to put even teen social media use in the same category as screens for young kids

Dangerous for different reasons. Unregulated screen time for young kids teaches their brain to expect stimulation at all times, and will usually increase their discomfort when they don't have it.

We try really hard to limit screen time to a couple times a week for max 30-45 minutes. Nothing saddens me more than seeing a totally content kid in public being sat down and handed a screen as the default (because it's 'easier' for the parent), depriving them of enjoying the world. Also see a lot of young kids who will cry and cry until they get it.