With the research i have done and reading various posts from different website I will give this a shot and try to explain.
As far a I can tell The ATTRIBUTE slider give every player a bump in ALL attributes across the board. So with attribute slider all the way up all attributes are boosted. So with this slider at zero it makes every player, play to their assigned number.
Trust me try it for 10 games and you will see the 4th liners miss the net from 5ft in front of the net and the true snipers pick a corner from the top of the slot..
This patch/tuner update is by far the best.
I will NEVER play another NHL series without the Attribute slider at zero
hope this helps!!