Why would playing power forward limit his passing? You can be a passer out of any position.
Would it not? I'm under the impression playing out of position would impact more than your scoring and defense.
He played PF in college in the post, his passing was based on playing that position from the high post (and low at times)
Yeah, but physically, he was not at a mismatch at PF in college. So he _might_ be more comfortable as a facilitator against SFs - you know, a lot of the guys who, like him, were playing PF/C in college ... 
I don't think this is true, Jeff Green was absolutely a mistmatch at PF in college. A NBA level athlete at his size and skill level is a big mismatch for the vast majority of college forwards. He was too quick for guys his own size and too big for smaller players in the post.
Very few NBA caliber PFs were around to punish him on the other end like what happens when he plays PF in the pros.
Yeah, I think this is the case (although I am not sure I am seeing the connection with passing).
I still think Green is a guy who we have not seen play in a situation that fits him for an extented period of time in the NBA.
In OKC, I think he was miscast, because he not only was playing out of position mostly at PF, but he also was playing with guys who really needed the ball as much as possible, and didn't allow him to facilitate.
And in Boston, he came into a terrible situation, where he was once again forced to play out of position almost exclusively because of injuries, and had to fit in to the system, and with some huge egos with very little time to acclimate...and while the wheels were coming off the tracks around him.
So, while I understand the idea that we have the book on the guy already, I do think there is a strong cases that there is still a decent amount of mystery to what he can do, playing on a team that really is based on good ball movement, which I think is a strength of his.
And lets remember that this C's system has had a way of getting the best out of players, and helping them perform better than they have elsewhere (Baby, Bass, Posey, etc.). I think there is still room for that to happen with Green, now that he isn't being thrust in the fire with no time to prepare.
He will still have to play a decent amount of PF this year, but more and more teams are playing SFs at PF anyways, so it won't make a huge difference.
Now, don't get me wrong, I am not saying Green is going to be an All-Star. I am just giving some credence to the idea that just because some skills didn't show up in his NBA career so far, doesn't mean they won't come out now.