Quoting: Brian2016
That's b/c Kadri got suspended when he dished out his one big hit! It's about sustained physicality and being tough to play against. CBJ steamrolled Tampa because of physicality, not b/c of talent. They were the best offensive team in the league that everyone picked to win it all. And they got dropped in 4 straight and it wasn't even close at any point after the 2nd period of game 1. I realize your point that there are always exceptions to every rule, but it's a different game in the playoffs.
I do agree that Playoff hockey is played and called differently, but the Leafs did have more sustained physicality than Boston. Boston basically won the series in game two taking cheap shots that weren't called and suckering Kadri into making a boneheaded hit. However, it was easily the closest series on paper, and it ended up the closest first round series, a bounce could have changed it.
My point is that all players hit more in the playoffs, including ones that aren't typically physical, case in point, Auston Matthews has more than half as many hits in 20 career playoff games as he does in 200 regular season games.
Teams get labeled as more physical when they win. It's a perception that has followed the bruins despite them being a middle of the pack team in terms of physicality. They won, and they used to be more physical, but they aren't anymore. Washington wasn't considered an overly physical team (despite being pretty physical), but then they win and it's all anyone can talk about. Chicago and Pittburgh were not physical teams at all.
What wins, is assembling a good core, and keeping them together while avoiding pitfall contracts and trades while continuously finding value to supplement that core. None of the recent winner loaded up for one or two good runs, all of them had years of being extremely competitive and then things finally broke their way.