I seem to remember reading an article that there are two distinct methods of making 'alcohol-free' beer.
One way is as you describe, to brew it as normal then 'denature' it to remove the alcohol. This would obviously require more time, effort (and therefore money) to produce.
The other way is just to mix the various ingredients together but without putting it through any brewing process. Theoretically, this would be a cheaper process than brewing real beer but at the expense of taste, based on my experience of it.
You should be able to tell by looking at the alcohol content. All 'brewed then denatured' beers still have a trace amount of alcohol left.
Heineken 0.0 for example, has a:
Heineken 0.0
Only those that are just mixed without any brewing taking place, are totally, 100% alcohol-free.
Some Muslim countries for instance, don't allow 'near beers' with even the slightest trace of alcohol in them, so will only sell the ones made by just mixing stuff together.