

The article is talking about banning social media under a particular age. This is enabled by the new Digital Service Act, and specifically the Age Verification Blueprint within the European Digital Identity Wallet. The same discussion is happening all across the EU exactly because the EU now has shared standards defined for how age verification will work online.
So while it’s true that counties can enact their own laws, like a US state can, they do so within a framework of European supranational regulation and they definitely cannot (easily) make national laws that circumvent EU directives. Well, they can, but the punishments and the hassle is severe.
But very specifically these discussions are popping up all over the EU because suddenly the EU is actually putting in place the machinery that allows it to happen. So yes, it’s a French discussion, but one borne of and fed by the European-wide framework discussion.
It may theoretically be a false assumption but in practice it’s really not. The MitID identification and signing framework of Denmark, and many other similar systems across the EU, is based entirely on “the device is personal, access to it is limited and the secure enclaves within them are trustworthy”.
You are correct that this framework is not designed for anyone who wishes to root their device or install a custom OS. In other words, it cuts out 0.00000000001% of the population. The colour of the app has a bigger impact than “oh no! We can’t support rooted devices”.