1) The Author didn't mentioned the criterion of reducing items. He just compared the effect of two reducing strateges by the classification changing proportion. I think the criterion could be designed by the examiner in practical.
2) MCAT is an more advanced method than the stratege he proposed. He just proposed the item reduction method by ranking discriminate parameter. MCAT should find the item with more information for classing the examinee. I think this suggestion can be tried in the future.