The weak gripping helps what he is doing with his arms, but it would work anyway. Even if the grips were strong, no matter. What actually is going on is blatantly obvious if a) your body is trained b) you understand aiki. The rest is a piece of cake.
Have to disagree to some extent. If uke was allowed to change his grip in accordance to Tori's movement (this would be a stronger position for Uke because it evolves like in real life), then Uke wouldn't be able to do that technique at all. A strong position will constantly evolve. That's the basics of Aikido.
All these type of demos fall under the false pretense that Uke is going to be a static loaf. They do teach a basic principal but like you said it's blatantly obvious and totally one sided.