The warning is always there, but only in the Employer account.
For employee roles such as Line Manager, if the Leave Application Policy allows negative balance, why warn? If it does not allow, then there is no need to warn too.
i remember it used to prompt that accepting this leave will put someone in a negative balance.
basically we want people to be able to go into a negative balance when there line manager approve them to otherwise we don’t want staff going into a negative balance hence why the warning is useful