If it follows the population median, than it means size has a minimal impact.
It's easier to score more when your linemates are talented. Oates-Hull, Trottier-Bossy, Oates-Neely, Gretzky-Kurri...
If only a few people in the population are that tall it shrinks the pool. There are way more big guys in the NHL and the NBA than would be normal statistically so obviously it's an advantage. You pretty much don't have guys under 5'8 in the NHL and there are loads in the general population.
There are so many more guys who are 6'1 and under, and there were many more in the league a few decades ago, so many more chances to be a star, bigger pool to choose from. McDavid and Lemieux were unusual but they exist. I doubt a quarter of the population is over 6'1, but considering the average player is now about 6'2 there are a lot of big guys in the league. There aren't that many big guys in the general population so more players are taken from a smaller pool.
I suppose size matters more on the defensive end, as well. Lots of stay at home D and physical but nonscoring forwards are pretty huge while most of the little guys, other than Byron, are scorers.