Wouldn't this result in a MAC Address conflict? I can't see this working on WIFI unless you were to able to fully establish a MITM attack. Furthermore, depending on whether any switches are involved, who knows where packets will be routed. In theory they will be broadcast, but smart switches could filter packets. I would imagine packet-loss would be very high in either case but I haven't tried it for myself
You have to remember we are talking about wifi here. You are correct in a wired network but the last hop can be thought of as a hub. All of the packets will be routed to the AP and the AP will broadcast them to all devices it's the NICs job to accept or reject the packtes and even if the MACs match as the packet moves up the OSI model they will be dropped by the legit NIC and yours will move the packets up. Now on a wired network you are correct lots of packet loss depending on L1 switches vs L3 switches, routers, etc.
Awesome, thanks for the explanation!
Ethernet and Wifi are broadcast. So, while two identical MACs are on the same local network you may run into issues. But, once the two MACs are on separate subnets (e.g. different coffee shops) then you'll be fine as the MAC addresses aren't routed beyond the local router.
But if you are in a different collision domain, you will have likely to re-authenticate.