The whole point of having an APP_DIR option is so that you can change it and things will just keep working. By doing $APP_DIR/.. you invalidate that by making assumptions about the parent structure. In particular something that could easily happen in the future is that you may not have write access to "$APP_DIR/.." You gotta do what you gotta do, but it is smelly.

Then you have fucked up your app config.

If user gives your app a directory to play with, exiting that dir via ../something is the last thing you should do, it's horrible malpractice that just causes annoyance

"distro scripts" near always just show direct path to /var/lib/something for data and /usr/something for rest.