I don't think the penalty discrepancy is unfair at all, Panthers have had the puck way more than the Bruins and outplayed them handily, you'll of course get more calls, the 2 legit gripes the Bs have are:
1. If you read the Athletic article on GI the Lightning callbacks make sense (both of them). I won't lie, the Bennett goal didn't. The league's explanation is that they acknowledge the push in but he wasn't going to make the save anyways, but that isn't the rule lol. Again, Panthers are clearly the much better team so I wish they could postpose some of these calls.
2. I don't really get how Benny wasn't suspended. Obviously it was a huge benefit so I'm not complaining but if I was a Bs fan I'd be annoyed lol.