A simplified scenario is as follows. Black moved his rook towards c1, but before he let go of the rook at c1, his flag drops. Since it is not checkmate yet, White wins on time, even though it is so obvious that it will lead to mate. The arbiter awarded White the win in that tournament.
That is a completely different scenario. In the OP's case, all moves are forced (with the first move being either knight). In your instance, white has a way to win in the position (a win by any series of legal moves), so when black's flag falls white gets the win.
Good point. I failed to inspect in the original position that Black cannot avoid getting mated. The correct outcome should be a draw in this case since there are no alternatives to the checkmate, but still, if the arbiter feels otherwise, then the game might not be declared drawn by the arbiter.
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While this given position is pretty artificial, all arbiters should come up with the same ruling in that position when white's flag falls. The rules are pretty straightforward in such a situation and it is easier for a human to determine if mate is possible for the side with time. I won't say that arbiters don't get it wrong sometimes or that all rules are completely clear-cut, but that one is.
all legal moves lead to a forced win for white, and people wonder why chess does not get recognized as a sport!