Yeesh. You should file a bug on this. To quote from TN2106:
"Files in AppleScript are considered to be objects. Therefore, properties and parameters that point to files should also be file objects. Do not use file path strings for this purpose. Similarly, do not have use file path strings anywhere use a file object, and let scripts use the path property of files if they really need to. (Cocoa Scripting got this wrong when it was first implemented. This is being corrected; you should not consider it as granting permission.)"
Two steps forward, one step back. <sigh>