Setting your Organisation default leave entitlements to 'No default - select when adding a new person', means you choose the leave types each time you add an employee. This is useful if your payroll contains several different employment conditions and you have multiple leave entitlements or rules.
Leave Loading - If you pay leave loading to your employees, you can select this as a default to be added when you set up a new employee. Or set it to 'No default - select when adding a new person' as per the above.