lol @ you thinking his argument has no anchor in reality when it is based on playing the actual games. Yours on the other hand has little anchor in reality as it is the one based primarily on your own opinion of who is better. So since his actually happened, it literally makes a lot of sense.
In your fictional example, yes the Devils were the better team. Because they won. On the ice. In reality. Where the game is actually played. As to why they won, of course injuries play a factor. Just like they do when the Wings win. It seems like the Kings would've been better if they were healthy, but who knows? We'll never know because that's not what happened. What we do know was the Devils won.
The Stanley Cup isn't won by who has the best team on paper or on your theories as to who is better. It's won on the ice.