... and to be quite honest, the statistical variation of fuel burn is probably around that sort of mark. The difference between a slick, in the groove operation with a visual approach, best speeds and avoiding unnecessary power changes, switching on the APU so that it is only available the second it is required, ..... and a careful, vectored approach, sticking to speed restrictions, not pestering ATC for climbs etc, being cautious with anti-ice is - I would guess - around 250 kg for a narrow body flight. The difference for inaccurate winds, vectors for spacing (departure, en-route and approach) is probably about another 200 kg. Once round the hold is maybe 200 kg.
Neither is the correct sort of operation. Remember the objectives of airline operation - "safe, punctual, efficient". The point is that half these effects are indeterminate, and half depend on the crew on the day. The effect of any fuel policy that will save less than 2% of fuel would probably not be perceptible over less than a season of flying.
Incidentally, do you know how much fuel you save by doing "two minute legs" in the hold? About 50 kg per hour in a B737. Again, the effect of this "economy" is so marginal as to be lost in the statistical variation of fuel burn.