I mean, in practice most Linux deployments where this could apply won’t have an entity that can be prosecuted anyway. Nobody is going to run around suing people who deploy Linux to their home PCs.
This will only affect vendors who sell Linux-based devices, for whom adding some kind of age flag to their user creation sufficiently that law makers don’t complain is likely a trivial addition. Say, e.g. Valve’s steamdeck, just implement it as part of the steam client (in fact, it’s already in there), or android.
A standard for this may eventually appear, but I doubt even then that NixOS would have to explicitly do anything.