I think it's good for demo purposes - similar in principle (tho applied to grappling holds) to when Wang Shu Jin would let people strike him. If you have your jin lined up and body connections stretched when someone puts a hold on you, it can feel to them like it's cinched in tightly and you still can move freely to escape or counter. It's not the same thing as being invulnerable to submissions - anyone can get caught by somebody good enough. Which I don't think anyone competent would argue against.
Per a conversation with Dan - that's exactly what he was demonstrating, as well as how to do it and why, and you're also right in that Dan says repeatedly that anyone can get hit or locked.