Physical defender to me means allowing the other team to have the puck so you can run into them, I would rather have the puck
defending in your own zone is more staying between the attacking player and the goal until your team can win the puck - skating/reach/hockey sense is what is important
and nobody clears the front of the net anymore, the rules don't allow it like it used to be - getting to the rebound first and doing something positive with it is what is needed - body mass is part of this, so is reach, quickness, anticipation, and actually having the skills to do something with the puck when you do win it
Nick Lidstrom played in a much more physical era, he didn't win all his Norris trophies by punishing guys in front of the net or in the corners
You're describing it like a defender's job is to just wait around until the other team either gives up the puck for no reason or one of the forwards helps out enough to strip it. I'm not sure if it is intentional or not, but you are massively underselling what defense actually looks like in the NHL. I 100% agree that defending is moving away from pure physicality, that you can defend without being a big monster, and that transition out of the zone is critical toward limiting goals. But NHL players are too good for your defensive strategy to just be staying between the attacking player and the puck.
Perunovich is well below NHL average in just about every defensive skill besides transitioning once he gets the puck. He has a well below average reach. His strength is well below average. His hockey sense when the other team has the puck is well below average. His gap control is below average. His shot blocking is below average. His skating is pretty good, but it is not so good that it allows him to consistently win races by enough margin that he avoids the (what should be) 50/50 battles that he loses 80% of the time due to his size. He doesn't clog passing lanes especially well. He's not effective at staying between the attacking puck carrier and the goal. He's also not effective at clogging passing lanes and checking his man when the puck carrier is away from him.
Being a physical player is not just about hitting the puck carrier. It is about winning 50/50 pucks, disrupting a player trying to receive a pass, and staying/getting into position to effectively clear rebounds. Most races to rebounds are decided not based on the speed of the players, but based on who won the better position before the initial shot was even taken. Incredibly fast players can win races that they shouldn't, but I haven't seen that type of speed by Perunovich. He's often either starting the race a step behind due to losing a physical battle or he's starting in the right position but off balance already as a result of the contact he took to get there.
Perunovich is skilled at transitioning the puck, but it is quite literally his only plus skill defensively. And what you do once you get the puck is absolutely not 50% of defensive play. I'm in favor of feeding minutes to Perunovich and I think that his strengths can cover up a lot of his weaknesses. But acting like he is just as good defensively as our other defenders because he can move the puck out of trouble is not accurate.