I think this is related to what O' Sensei referred to as "empty mind."
It is the concept of being so focused that you are so aware of your movements that they become as natural as breathing, according to O' Sensei.
I believe that mushin (often translated as "no mind") actually means something rather different than a state of hyper-focus...in fact, you might say it's almost the direct opposite. Ref. Takuan Soho, "The Unfettered Mind".