Honestly I always assumed the UN number was just for the freight companies and customs paperwork. It tells the shipper how dangerous the thing is so they handle it right. For us buying consumer stuff at the tent, the retail packaging is what matters more than hunting for a UN stamp.

That said if you’re the type who stores a serious stash, having it in something that’s rated (or at least sturdy and dry) is just peace of mind. I keep my cakes in a cheap metal ammo box and haven’t had issues. The UN marking on the box that came from China is definitely not something I’d stress over as a consumer.