The ideas behind 6σ and TQM and so forth can be applied to the development of a new business process, but measuring bug rates in the support software is only a tiny part of the problem.
I never suggested that you shouldn't count bugs. The whole problem is that I see lots of "6σ Black Belts" who think that all they have to do is show increased numbers of test cases, and decreased defects, and everything is A-OK. The question of whether the entire process is "pointed in the right direction" doesn't enter into their calculations.