As long as your vehicle is in good running order, it might not be bad. I'd also wait until the vehicle had reached the normal operating temp. Personally, I don't do it at stoplights, but I will do it if I'm sitting anywhere else. I also avoid the drive-through now (they F*ck you at the drive-through) and try to combine stops.

On road trips, try popping it into neutral if you're heading down the mountain - you may coast at the speed limit or higher. Just make sure you're not riding the brakes to do so.

But this does make sense - vehicle dependent. Warm starts should be set up differently with the advent of fuel injection, so it does make sense.

I though turning the car on and off caused more fuel to be used every time?

With carburetors, that's definitely true. With modern fuel injectors, maybe not so much. However, my guess is that it depends on the vehicle.

It should be pretty easy to check - reset your trip odometer each time you fill up and drive as you would on average. Calculate fuel used and note miles/tank on average. Once you've established a good baseline, do the same with doing this particular plan. As long as your driving habits don't very wildly, it should be accurate.