Check this illustration:

[1] BEFORE rolling, the 1/2" inside fender lip looks like an ell, with your tire near the horizontal leg --> L

[2] AFTER rolling, the 1/2" inside fender lip has been pushed up resembling a vee --> V

You can see this gives you additional lip clearance from the edge of the tire AND if the tire does occasionally rub, it won't get "shredded" from the "L" knife-edge.

Hope this helps.

Brian