The article is basing it on skill vs luck and that is BS. You are saying if I understand correctly that it is based on parity.
The closer you are to parity in skill the more that luck is a bigger factor in determining who wins.
If everyone is equally skilled, luck will push you over the top. In the NBA there is more skill heavy and skill-free teams, so luck is not such a big factor. You also have a huge amount of scoring chances in the NBA vs the NHL, which again, gives the lucky NBA plays less importance, and more likely to even out.