After no penalty minutes in his first ten, Marchand has brought out his well-known pest qualities in the last couple of games. However, with a reputation like Marchy, sometimes opponents get more leeway against you.
There easily could have been a penalty called on this play, as many penalties are called during scrums after whistles and periods all the time. At the same time, it does look like Marchand was attempting to hit Whitecloud, who, in turn, is trying to avoid it and takes him out.