Yes, when your coasting the car can't be at a standstill, you still use the steering wheel and what not which draws power...when you sitting still and nothing at all is running then your idle drops that low.
however In neutral, the engine is at idle speed, meaning the throttle is OPEN. Leaving the tranny in the proper gear according to steepness of the grade means the throttle is CLOSED if your foot is completely off the gas pedal. That saves gas and is also a lot safer when the engine is doing some braking.
if you allow your car to slow you down, you do 2 things, first you are not wasting energy by using your brakes, and when the engine slows you it goes into a super lean mode (usually air fuel ratios above 17:1, sometimes far higher). this does no damage your engine, so don’t worry. However, if you put the car into neutral, the engine must maintain itself so it usually goes into a 14.7:1 air fuel ratio, therefore using more fuel while idling to a stop then [than] while engine breaking.”[braking].
There are many debates wether or not nuetral saves you gas but i find more that lean toward it consuming more. Just my two cents.