I'm not going to dispute that the accuracy/consistency of BBs downrange is based on a myriad of factors, from BB materials down to barrel cleanliness.
However, I do not tend to favour one manufacturer over another. BBBastards have been quite good to me, but I'm more than willing to try out a bag (or two) from another manufacturer to compare. If it performs better, I'll move over, else I stick with what is working.
By your own words:
While the visible factors are easy to see, there are a number of other manufacturing processes that can affect distribution that are not visible - only the result - a good BB.
And so, I will continue to test and compare.
(Disclosure: Although this is my first year back in the game after a long, long time - and I'm still learning the new technology that has sprung up during the intervening years - that does not mean I am incapable of doing my research in an unbiased manner. At the end of the day, one of the few things that matters to me are the results, and if they meet my - and only my - expectations.)