It's got a lot to do with orientation and positioning: the angle/distance from a faceoff dot, for instance, is different from NHL ice and Olympic ice.
Markings and stuff like that are landmarks for goalies to figure out where they are and where they should be.
So if a goalie is used to being in x position in the crease and y distance from the net for a shot from that area on Olympic ice, it takes time getting used to where they should be in that situation on NHL ice.
You'd think it would be just as simple as centering yourself on the puck, but even goalies who've been in the AHL for a while are still tapping the posts of the net every once in a while to make sure there positioned right. Sure, a lot of it is a habit, but they still feel the need to do it.