Broad based benefits tend to receive more public support. Just tax those with high incomes to get it back. Otherwise the bumpy effective marginal tax thresholds (which increase and the decrease again as income increases) end up incentivising gaming the system by shifting when income is realised.
Presumably the optimal strategy if you have retirement income within the range where you face a 15% clawback might be to withdraw extra income one year so that you can avoid the clawback the following year, since the higher marginal tax rate would be less than the clawback saved.
Presumably the optimal strategy if you have retirement income within the range where you face a 15% clawback might be to withdraw extra income one year so that you can avoid the clawback the following year, since the higher marginal tax rate would be less than the clawback saved.