DC3.
I understand the points made about leave accrual. However at present the situation is working for free equals a loss of two days leave. I don't believe it is ethical and I haven't checked legislation to see if it is legal. Part of me thinks the situation is that volunteers have in effect taken unpaid leave then worked as a volunteer. Thereby losing leave and accruing nothing. It may be that the payroll computer cannot comprehend the concept of unpaid work.
But as it stands unpaid work volunteers have lost annual leave, which I hope will be corrected.