IMHO this is nothing to do with noise, it's a marginal gains thing.
More time spent at idle thrust, 1000' to TD slightly shorter, so 2 pints less fuel each approach.
1 aeroplane not much, 100 aeroplanes quite a lot, 1000 aeroplanes - departmental greeny wonk gets pat on the back for his lovely spreadsheet, and bonuses all round (the office).