As an example - if a person was bullied in school, and has subsequently built up impenetrable walls in relationships, it could be helpful to re-enact an act of bullying in a safe setting. Only this time, the person is fully in control and can create an alternative ending - e.g. by letting an 'ideal friend' or an 'ideal parent' join in and stop the bullying. Now a synthetic memory is created - sure, it does not replace the old memory. But now you've got to experience that there are different outcomes possible, now you feel more protected.
The power of this method lies exactly in the experiencing. Before being exposed to this approach I thought my problems would go away, if only I could really really understand them. Now I see that experiences can be quite a bit more powerful than words and concepts. I can also see where all the rituals in human cultures are coming from.
What is created is the knowledge that a different experience is possible. Not just textual knowledge, but lived knowledge. Examples of the correct behaviours that you may see in movies or read in books or even witness in your friends are still not your lived experiences. This approach changes it.
This being standard talk therapy and not what grandparent poster was talking about, so the approach he talks about doesn't sound pitiful. Your emotional system (which drives a lot of cognitive behavior) responds to things differently than your logical self.
Also your post seems pretty harsh and judgey for someone that hasn't tried what they've tried, and potentially hasn't had the same life experience.