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.
Demos are demos
But since you decided to talk about real time applicability.....I am not changing one single comment or opinion. What I do in solo training, I do in kata, I do in drills, I do in sparring, I do in fighting. The only reason it looks different is due to speed, and the type of attacks someone brings. IP/aiki is not only fluid, it is hyper fluid and produces power and aiki non-stop in motion, and what SHioda is demonstrating can fit the bill if you know what you're doing.
To be fair, I have yet to see, feel, or meet an Aikido or Daito ryu person of any rank who both understands and can do, what I just said to you to the level I am talking about. I'm not saying they don't exist, I just have never seen it.