Well I would say what you are doing is what I would call true relaxation and when you do such you become more aware of center etc. No more significance than that. The more you do it the better you get.
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.