Point in your favor: They have apparently NEVER stated it was exclusive, just that they WANT to use the money to improve the game. However I will say they also have specifically stated that the data center move for NA and the expansion of that data center were done with cash shop money. So you're right in that there is no ironclad statement to nail them down for it and it's possible SE is just pocketing all the money and frittering it away on other projects, it's not like we've never seen benefits from it.. at least we've been told the game benefits from it. We also have a statement from Yoshi (as idealistic as he really is, I get it) stating intent to use the profit for the benefit of FFXIV.