Correct and consistent information is the best information!
I agree totally with you there.
My thinking behind including the 'bits' is that you bring the frames up to equal functional levels and therefore can make a 'if I swap frame A for frame B the change in weigh to my bike is C' comparison. 'Bits' can be added or subtracted on paper to equalize any 2 frames for comparisons, but that doesn't tell us if one manufacturers frame uses lighter or heavier add-ons.
I'm always cautious using the manufacturers data. I would assume most bike manufacturers are just like the manufacturers of other engineered products and the data they share is 'marketing' data as opposed to 'engineering' data. I'm sure a few do let their engineering data out, but I assume they are the exception and not the rule.
This is, IMHO, why thier published data doesn't include the 'bits' - so they can advertise the absolutely lowest number with respect to their frame weights.
At work when we compare our vehicles to competitors we always group individual parts into function subsystems. Then when we do performance/cost evaluations we are as much apples to apples as possible (it's almost never perfect). Just taking part vs part leads to bad comparisons more often than not, is my experience.