This used to be a problem users accidentally caused because of the way mover worked at one time, but since mover was changed yours is the first I have heard of someone actually doing it deliberately. Most people want their appdata to stay on cache because many applications frequently write to their appdata and any writes to array disks also involve writes to parity, thus keeping 2 drives spinning all the time. Also, there have been reports of some apps not working correctly unless their appdata is on an actual disk instead of a user share. I think it has something to do with hard links.
So in summary, the recommendation is to actually put appdata on a cache-only user share, and then make all your apps refer to it as /mnt/cache/appdata.