I think the significance of the two settings as well depends upon how low a profile the tyre you have is, in combination with the tyre make and the wheel diameter.

On most of our cars we tend to run comparatively small tyres by modern standards with tyres that have ( by runflat standards at least ) comparatively flexible sidewalls

I think on the latest BMWs that run large diameter wheels with pretty low profile rears ( 35 profile ) AND that are also runflat so hence have extremely stiff sidewalls they have had problems with the stock camber killing the inside rear shoulder quite quickly at the back. This happened to someone I know and his toe settings were well within spec but the rear camber was at the extreme end of the BMW spec range ( -2 deg -ve ).
Presumably they've set it like that from the factory for handling reasons but the trade-off with the stiff-sidewalled runflats has been the inner shoulder tyre wear. I suspect with normal tyres the discrepancy between inner/outer shoulder would be less as the tyre would 'mould' itself more to the road surface as suggested by Tabetha.

I think it will be down more to toe settings than camber on a stock Sierra that is lowered but I think you'd also have to take into account the wheel diameter/sidewall stiffness of the tyre make as well.
I wouldn't be surprised if a stock size 15" wheel with something like T1-Rs suffered much less inner shouler wear than a 17/18" wheel with something like a Toyo 888 or Yokohama AVS over the same mileage ( assuming the toe was correct as far as possible )