You think it's a risk because of the statistics that are screwed from many years ago when the NHL was all about size, grit, aggression. When goons played on the same line as their star player. Look at guys like Provorov, Morrissey, Honka, Rielly, Dumba. I know only Honka is 5'10, but these guys are smallish defencemen that are succeeding in the NHL. Smaller defencemen might have been failing in the 80s, 90s, early 00s, but it's not the case anymore.
My point is that size was the biggest concern for Hughes and Pettersson. Nobody questioned their skill, but their flaws were strength/height. Otherwise, they were the BPA. We took the best, most skilled players. That isn't up for debate. I haven't seen a centre that weighs less than 170 pounds, that's a risk drafting someone under 170 pounds.