Whereas Loki is from a culture that teaches self-defense and prizes warriors, from a very young age. Best way to avoid accidents with weapons and 'kids' is to teach 'em how to use it responsibly. ;)

Besides, Luz is an adult in some cultures already.

Would Red Son also be capable of making actual throwing-card-knives? Because Loki's putting an order for that too, as that'll be a Yule gift for Seto.