Sugino may be managing their tolerances to a smaller variance. Shimano BB are made for gears and crossed over chainlines so will not care as much about how consistant their products are. Sugino prob cares a lot more and will reduce the variance in their products (i.e. impose a tighter manufacturing tolerance than the industry standard) which will result in repeatability between parts (i.e. better chain line as advertized). Remember there is industry tolerance and there is manufacturing variance. How you manage the variance depends on what your audience demand and how much they are willing to pay.