/mnt/user/appdata under normal circumstances includes everything that is actually on /mnt/cache/appdata, however, /mnt/user isn't directly accessing the data on the disks, it's going through the special unraid filesystem which sometimes doesn't play well with some apps. Also, /mnt/user/appdata isn't guaranteed to be ONLY on /mnt/cache/appdata, /mnt/diskX/appdata if it exists will also be included in /mnt/user/appdata