No, it seems possible.
Imagine the game being run somewhere. Like a theatre inside a black box.
Running into this box are input streams - these are the (controller) inputs from each player.
Running out of this box are the output streams - the game display (plus, because Brawl people don't have any **** clue that a smash games needs all data preloaded, a whole lot of other info, such as Sheik's data).
Suppose the streams to and from one player are much longer than another's.
Then the theatre inside the black box will still run - it has no idea how the inputs got there; it just processes them in the order they were input, and plays the game.
It also can't be held responsible for how much lag there is in the feedback. It sends the display off at both output streams at (in all practicality) the same time, but one player may be observing the game state 50 ms ago (and what he input 100 ms ago), while the other may be the same for 500 and 1000 ms.
So it's certainly possible.
It's anyone's guess why the hell it is actual.
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There's also the chance one player is more tolerant of lag than the other. Just recently, I was getting pwned by a Samus in a game where I was having a full second of lag.
I'm like.... dude, he's playing a mean Samus. With 1 second of lag. That can't be right.
In any case, I had and have no desire to adapt to that much lag so I quit.
What ticks me off is how you can only measure your ping to people who are OFFLINE. That's just stupid.