Thanks for this comment. True, if you really don't know that you shouldn't say XYZ then you won't understand using this technique as well.

But often we do things we somehow know are problematic. And as I write we don't always remember. To prevent those things the technique is useful. It's also useful to remember all the questions asked for example. And you can verify your answers often easily using Google or this community.

And you're right: mock interviews or direct feedback can help you with things you don't know. But it's not always easy to get access to them. Most companies don't give feedback. And you might not have friends who quality for mock interviews