It means that at 5'7 if you are a "good" playmaker, your good playmaking isn't as effective as the "good" playmaking of a player who is 6'3.
Do I need to explain why that is? I'll do so. If you are 5'7, your space gets crowded out easier, you have a harder time creating space, it's easier to strip you of the puck, you are usually stripped of it quicker, and you have a crowded view of the ice through the trees.
Because it's not as good as a 6'3 player with good playmaking, it'd be stupid to treat the exact same ability in a vacuum for a 6'3 player like you would a 5'7 player. Thats why I think when you are 5'7 and in a vacuum you are good in an area, it probably isn't accurate to call it good. It's probably not going to end up being a real asset at the NHL level, if it's only good.