This feature is a part of BlackBerry Balance this is a feature that you can only modify in BES when it's got Mobile Fusion installed. Apparently RIM installed BB Balance into OS 2.0 along with it's default settings; there is no way to adjust these settings unless you have Mobile Fusion installed on your BES 5.0.3 (non-Express) server.
Here is the info I found on it from crackberry.com BlackBerry Balance | CrackBerry.com
So no its not related to ActiveSync, and you can't modify the settings until Fusion is out and you have the big bucks to pay for it. You can however disable BB Balance on your playbook all together.