This definitely makes sense, since otherwise you'd never fill up the class.
I was referring to the A multiplier being sometimes less than one, which I've heard some schools do (i.e. accepting only ~80% of the class initially and the remaining ~20% are taken off the WL). I have no clue what the strategy is there though (as opposed to accepting the entire class size first and pulling from the WL when those accepted applicants rescind their acceptances).