Not many martial artists have understood this principle. What Musashi meant is that naturally there are thousands of pre-fight-positions in the martial arts. Some are more or less sensible, some are artistic, but do they come natural to you? Only natural movements allow you to move freely
You practice natural positions all your life. For example, if I want to calm someone down, I take my hands up with my palms facing to the front. By doing this I don’t look aggressive. This way I can allay someone, but also in case of a attack of my own I don’t forewarn him, because I look natural and not aggressive. From a defensive point of view I have good protection.
Therefore in P.W.C. we say:
You can’t always choose in which position you are attacked in in real life. That’s exactly why we use elaborate, natural and seemingly non-aggressive positions in P.W.C., or else you lose the so important moment of surprise.