There are no different levels of intensity to centre. There are no different levels of intensity to one point. Neither are there to centre line or koshi.
Fighting? Combat? Sparring? All have certain things in common which when recognised are merely the same. The only true enemyto Aikido is self.
Graham, have you experienced actual combat?
I believe Lynn Seiser has, along with his long experience of aikido.
You might want to reconsider his comments.