Great question, and yes it's the same idea! This is indeed a necessary. Therefore, if the necessary is not triggered, that's sufficient for the alternative to happen! Another way to say that is that Leung will ALWAYS be on desk duty earlier than Flynn except for if Leung is on Saturday, in which case he doesn't have to be earlier than Flynn. And indeed, it's impossible in such a case because Saturday is the last day of the game.
Therefore, unless L is on Saturday he is pretty early in the week as he has to be before F and some others, and F has to be before some other pieces too!
I hope this helped, if you have further questions don't hesitate to ask!