Yes, this idea. My understanding of the original idea was that someone wanted to kill a samurai. If the samurai got his sword out, that became significantly harder. So they would ambush him with a surprise attack. The first attack was to grab the arm that would go for the sword, before the samurai knew he was being attacked. This grab was immediately followed by taking his balance, breaking his structure, and taking him down... all while the other attackers joined in.
Brought into modern times, if one were to attack a police officer, one might want to prevent the officers hand from ever getting to the gun. If you were going to attack someone who was carrying a weapon, you might want to prevent them from getting their hand near their weapon. As the officer or person carrying.... if you get surprised and caught off guard, thats where these escapes come in.
You are right, if you suspect that someone has a CCW and you grab their wrist, and stand there statically waiting to see what they do.... its a very ineffective technique. But, if you grab the wrist, break the balance and structure, hit them in the face, throw them on the ground, while not letting them get their weapon... things get easier. But also it becomes a lot to have a beginner practice on their first day. So working on the parts separately can be good. But, you do have to bring the parts back together.
The main failing I see with "shake my hand" or "grab my wrist" techniques, is that we take them so, extremely literally. We forget to make them real attacks. Its okay to train them statically to teach beginners and to study fine details. But that must be paired with resistance type training. At the end of the day.... its not the technique that is important, its the principles and ideas you ingrained in your body together with your experience of adapting those under the pressure of different attacks.