You may know that the NHL changed the forward-passing rules at the beginning of the 1929-30 season. To counteract scoring levels that has dropped to miniscule levels, the league decided to allow forward passing in all three zone, where before it was allowed only in the defensive and neutral zones. However, they did not place any restriction on players entering the offensive zone before the puck carrier. Predictably, scoring levels skyrocketed. In the 1928-29 season, the average NHL team scored 1.46 goals per game. Through the games of December 19, 1929, the scoring level had risen to 3.45 per game. At this point, the league decided that they had fixed the problem a bit too well, and instituted what are essentially the modern offside rules, preventing an offensive player from entering the offensive zone before the puck. For the rest of the season, NHL teams averaged 2.74 goals per game.
Due to these rule changes, some people cast a very suspicious eye on the scoring totals of players in 1929-30. Even though Cooney Weiland and Dit Clapper, two Boston forwards, finished first and third in league scoring, their finishes are often discounted because of the "cheap" way they piled up their points, using rules that the league ultimately decided were unfair. Indeed, the regular-season dominance of the Bruins (38 wins in 44 games) as a whole is typically discounted, for the same reason. Evidence is inferred from the fact that Weiland and Clapper, and the team as a whole, performed much worse relative to the league the following season.
But that's a simplistic view, and relies on a superficial view of the numbers. The leagues adopted the modern offside rules only 30% of the way into the season, meaning that most of the year was played under "fair" forward passing rules. Moreover, the Boston Bruins were a better team after the modern offside rule was put in place, than they were before it, in 1929-30. And that was no mean feat, since they had compiled a record of 11-2-0 before the change (an .846 winning percentage). After the offside rules were readjusted, they went 27-3-1, a percentage of .887. While league scoring as a whole dropped by 21% after the adjustment, the Bruins went from scoring 4.08 goals per game to 4.06. Boston wasn't even leading the league in goals when the adjustment was made (being second to Ottawa on a per-game basis), but ended up dominating in the offensive department, scoring 26% more goals than the second-best team. The key to their increased winning percentage was that their opponents had a much more difficult time generating offence, as they allowed only 1.97 goals per game compared to the 2.85 they allowed before the switch.
Both Weiland and Clapper also picked up their games after the adjustment. Weiland had 9 goals and 20 points in the 13 games before, and 34 goals and 53 points in the 31 games after. Clapper had 15 and 16 in 13, and 26 and 45 in 31. So Weiland's per-game production increased from 1.54 points per game to 1.71, and Clapper's went from 1.23 to 1.45.
So the Bruins certainly had a flukey season, in the sense that a lot of things had to go right for them to compile the results they did. But we can absolutely not write them off as a product of unfair rules changes. Indeed, in some sense they were the team that took the least advantage of the unfair rules, since what they scored before the adjustment was the same as what they scored after. They earned every goal they got, and should be remembered as such.