While the OP hasn't provided any details, there is a scenario where the member may have burned all their leave already no through their own fault, and not necessarily their immediate supervisors fault. The member could have been on parental leave since 1 Apr until end June, and only had enough time in to have earned 20 days leave. Unit goes on 3 weeks block leave for the summer requiring 15 days annual, he can only earn 14 that FY, so used all his leave, plus 1 short, to make it through the summer, as per Div orders.
But yes, someone should have recognized this and maybe used some common sense and not forced the member on a full 3 weeks block leave.