No evidence / proof of this? In my opinion, you don't need evidence to account for something you can conclude by simply utilizing common sense. I wasn't even talking about Chara.
Take a look at the heights of the players who played in NHL as u-19 and then consider that the average height in NHL is 6'2".
For top 10 u-19 players in NHL all-time scoring, their final height:
6'0", 5'11", 5'11", 5'11", 5'11", 6'1", 6'1", 6'3", 6'0", 5'10", 5'11"
From top 20, we might also add Jeff Skinner, Ryan Nugent-Hopkins and Nathan MacKinnon because they were the only ones out of those who played in NHL at that age post-cap. They are 5'11", 6'0", 6'0". Tyler Seguin and Steven Stamkos are also known for playing in NHL while that young and becoming stars. They are 6'1". Out of this list of 15 heights, only one is above average. 14 are below. Oh, I forgot Matt Duchene from the top 20. He was 5'11". So 15 below average.
You'd also have to compare it against something like the top 10 all-time seasons by players, and what height they were. And the only giant among that bunch is Mario. Almost all of the top 40 indvidual seasons are below 6'3, outside of Mario and Jagr.
Is this "evidence" of anything? No. We aren't in court. Feel free to disagree with me if you wish.