"everything works fine" might be overstating a bit, but what happens to packets you weren't expecting when you don't have a connection open for them to go into?

"everything works fine" might be overstating a bit, but what happens to packets you weren't expecting when you don't have a connection open for them to go into? They probably get ignored by the network stack. Worst case scenario, the router/service endpoint sees your connection responses and the other party's strange NACK responses, but I honestly don't know enough about how it works to say "everything works fine" I'd guess that connectionless protocols will work fine and connected protocols will also work fine. The truth is probably YMMV by protocol, but there is truly no way for the wifi router to detect this is happening or isolate the redundant stations - it's an unencrypted broadcast. The only way this goes sideways is if a connection protocol is engineered to make it go sideways when you try to do that. I'm pretty sure that any such protocol which succumbs to any unencrypted (or incorrectly keyed) traffic that isn't from the designated counterparty is insecure to begin with. It should be resilient against DoS, so most protocols aren't going to have that vulnerability. Again, I'm guessing, but I'd hope.