A common cause of nearsightedness is near-point stress. Ortho C is designed to reverse the effect of near-point stress. If the eye became nearsighted by some other factor, ortho C may not adequately deal with it. Thus the eye has to be within the myopic model (that it became myopic on its own accord due to near-point stress and not by some other offsetting factor) before ortho C can treat it.
The crystalline lens needs to flatten first before the myopic eye can retract. It's the opposite of how the eye became myopic (due to near-point stress): the crystalline lens had bulged excessively, then the eye had to elongate to alleviate the tension of the ciliary muscle. The crystalline lens needs to initiate the reversal process by flattening first for distant focusing. The eye would become less myopic to alleviate the excess effort imposed on the ciliary muscle to compensate for the myopic shape of the eyeball as well as for the myopic shape of the lens.