In the real world, some financially astute people on small to moderate incomes with an ARF or AMRF who can choose their total income level by varying their yearly withdrawals, do actually set their total income to exactly match the tax free income threshold or to maximize their 20% tax band level. I know people who do this and I have helped them to calculate their optimal income level. These people are very appreciative of any tax saving and the 308 euro that you have correctly calculated would be of greater value to them than to Revenue.
No doubt you will be surprised to learn that people like this do actually exist.