Graham, as someone who is doing this training, I must respectfully disagree.
Where I agree is that a specific form of relaxation is key to doing martial arts - of course, this is not new, it's part and parcel of judo's "maximum efficiency with minimum effort" and presumably predates that - the idea of only engaging what needs to be engaged.
However, there is something much more active being done. What is being described is literally learning to isolate and work with specific body structures that are not those most of us have been aware of feeling much less being able to engage.
Which bit of what I said do you disagree with? David is practising yes? He's getting results yes? The more he does so and gets confident then the more he will relax and thus see even more. That's what I'm saying. I'm sure he must be practising whatever else is involved too.
Relaxation is one of my preconditions but don't think I mean that 'maximum efficiency minimum effort' saying and the concept of engaging only what needs to be engaged. No, that's not my way.
Anyway, time will tell. If he has a specific technical question on what you are practising I'm sure he'll ask the relevant question to the relevant person.