Does the one coat paints really work?

We had a burnt sienna (orange) color in the entire main area of our home. We chose a light grey Olympic one coat and it worked really well. One and done, even over orange.

I used the one coat paint and the paint and primer in one. You see the commercials on TV. Watch closely and the paint rollers are really loaded with paint. It will cover with one coat that way as any paint would. I also noticed that the finish doesn't really look good. So I primed one area then painted and noticed the color was more bright and vibrant on the primed wall than the one not primed. They just put in more paint solids in the paint, call it one coat coverage, and raise the price. I'll continue to prime and paint.

I have great faith in Behr Premium paints...but I had to give two prime coats and two finish coats of an ivory-toned paint to cover a Ralph Lauren gray. I think it depends what color you are trying to cover.