I wasn't aware of such a policy. Seems strange, because they definitely have no problem with flight deck shots (I'm working to upload one I took over the weekend), outside shots while entering the plane, and shots through the windows in-flight. I've never had any remarks, and I am sure F/A's saw me working with a camera on several occasions. I guess it depends on how suspicious you look
But then again, I've never tried a cabin view.