I'm finding the toughness argument fascinating, and want to attempt to add some perspective. I have to thread a bit of a needle here as I cannot divulge anything with internal Bruins data and/or discussions, so everything below will be based on publically available data.
I don't think I'm speaking out of school when I share that the toughness discussion played out in every pro meeting I attended (7+ years with the team). In particular, many in the room were concerned about toughness and physicality in the playoffs. I am going to focus here on postseason play, and how it differs from the regular season.
There's a perception that the refs swallow the whistles in the playoffs, but is that actually true? Looking strictly at the number of penalties called, it is not. Over the past 3 seasons, teams have averaged 3.20 power play opportunities (and PK's obviously) per game in the postseason vs 2.97 PPO/G in the regular season, an almost 10% increase. Quick aside here, but in the 5 seasons prior to this penalties per game in the postseason and regular season were close to even. But I do not think the number of penalties tells the whole story.
Hits (which I agree is a terrible stat, but the following also is true using more accurate internal measures) increase by over 50% in the postseason. Over the past 3 seasons, NHL teams have averaged 33.5 hits per game in the playoffs, while just racking up 22.1 hits per game in the regular season (+52%). This matters because there is a very strong correlation between hits and penalties in the regular season. Looking at all NHL players with over 500 minutes in a season over the last 3 years (almost 1700 player seasons), and we see a correlation (r) over 50% between the number of hits a player had and the penalties they committed.
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On the above, hits are on the Y axis, penalties on the X axis. FYI, the outliers in penalties (above 8) include Brendan Lemieux (twice), Nicolas Deslauriers, and Nick Ritchie, outliers in hits (over 20) we have Ryan Reeves (twice), Matt Martin (twice), and William Carrier. No surprises there.
The above strongly suggests the game is called differently in the postseason, with the refs letting a lot more go. I think this is to the detriment of the game, and I won't even start on the Blues hits vs penalties numbers in THAT SERIES!
Does this mean teams need more toughness in the postseason? I'll withhold comment, but do think it's a fucking joke to have different rules in the playoffs.