It's not my logic, it's proven fact that stretch does provide tractional benefits.
On solid rear axle cars, like my corolla for instance, a little bit of tire stretch on the rear would have much the same effects as adding a static negative camber because of the stiffer sidewall and the new geometry of the sidewall from the stretch. Stretching tires originated from this very same idea, long before people really did it as an 'aesthetic' thing. People were putting wider wheels on cars while keeping the same tire size, only to find that the new stretch was increasing their skidpad numbers. One study found that a tire that was manufactured for a 7" wide wheel, saw an increase from .96Gs to .99Gs, when it was mounted on a 9" wide wheel.
Take a good look at F1 cars
They're known to run around -5 degrees of camber and if you look, there's plenty of tire stretch present. People argue up and down Camber is stupid as well, but it has it's reasons aside from the common myth of just destroying tires.
http://www.blogcdn.com/www.autoblog.com/media/2011/02/web630-rb7.jpg