Sure, if you go in with the idea that the ban won’t impact their social media usage then it obviously follows that it won’t impact their usage. And that might be true for a while, but:

• Declining usage compounds and any barrier to entry drops users
• The single largest factor in platform membership is peer membership, and the most influential peers in adolescent development will always be real life friends
• A cohort aging up doesn’t mean that the next cohorts will automatically follow. Late millennials weren’t tied to Facebook, Gen Z wasn’t married to Snapchat, a drop in TikTok usage will eventually precipitate a need to migrate somewhere else
• Global social media usage, by human screen time, has been declining from its 2022 peak (excluding a North American exception), with the largest drop among younger users

Putting all of this together, it seems very plausible that child bans could hasten this decline. It would probably work twice as well if more public money was directed to alternatives (third spaces, clubs, etc…).