Why does leave not accrue when it is configured for a specified amount of hours to accrue per month?

Why does leave not accrue when it is configured for a specified amount of hours to accrue per month?

Employees will not accrue leave, if, for example, the Annual Leave type is configured to accrue 6 hours per 1 month.

      Navigate > Configuration > Human Resources > Leave Administration > Leave Scheme Parameters

      

When leave is configured using an hourly accrual rule, the system is designed to look at "days" or "hours" (not "month").