Originally Posted by ade

In this case it should be okay. but did you test correctly?
You must use the sh shell and be user.

echo $0
must return: sh
id
must return: uid=29999(user) gid=29999(users) groups=20(dialout),29(audio),44(video),670(pulse-access),29999(users)

Then do you still get /var/tmp as a value for TMPDIR?