Nevermind, looks like I managed to break tapatalk.
How so?
I tried to back out of TFES so I could search for more forums to join and the app promptly crashed. So I force stopped it but that did nothing. Restart, nothing. So I just uninstalled it. And if it isn't going to use less data then I've pretty much run out of reasons to bother with it.
Apps force close sometimes but I can tell you that I haven't had tapatalk force close on me. Not yet anyway. I'm not sure why force stopping followed by a restart didn't fix it but restarting your device may have fixed the issue.
In any case, I think it probably does use less data because once it is connected to the server it doesn't have to download all the graphics on the forums each time it loads. Only the avatars, images within posts and texts. As a matter of fact I saw an option in there to not download any avatars or images if you have a slow connection too.