[grayfaced]

It's not a firewall acl, it's a port forwarding rule. In a NAT, UDP connections you initiate will be added to NAT table temporarily to handle replies. Nintendo's port range covers all the ephemeral ports that OS will naturally give to UDP connections. So your computer may attempt to start a UDP communication but the reply traffic will be forwarded to your switch instead of using NAT table. So nothing else can use UDP properly. That DNS request to port 53 has a source port of 42981 (for example), and the switch gets the reply.

I'm not sure if most routers prioritize port forwarding rules or NAT tables. That's really up to implementation.