My theory is this-
JS, IS and PA affect shot selection. THe more IS the more inside shots attempted. The more PA the less bad shots taken. The more JS the more bad shots taken (since outside shots are usually bad shots in this GE ;))
From pure observation (no hard data) JR also alters shot selection. If a player has high JR, he will try for more long-range shots and since OD is universally overtrained, he will fail most of the time. If a player has low JR though, he will try for more midrange shots and be also more successful. If you play Motion with a PG that has low JR, but high JS and DR, he will mostly drive and shoot midrange shots. If you put a JR monster on same spot, he will mostly shoot from distance. It's also worth noting SG spot will almost always take more longrange shots than PG or SF.
but he takes the longrange shot, cause he had the same chanche to convert then a player with less JR from a closer distance(the shot this player takes instead), so it is ok again.
And yes offensiv better player, will take more shot so the same player will maybe even take those shot extra but in general the team can be more selective in their shot cause they got promising looks more easy and often. So JR is definately no disadvantage.