Since getting into MF last year, I see this a lot. It does seem like Ilford is more prone to it than Kodak, but then again, I'm generally using Ilford in my folder, which means I'm loading and unloading outdoors quite a lot. My Kodak film use is generally in my RB67, and I usually load up a few backs indoors before heading out to a shoot. So there's enough variation in technique there to explain the difference.

Anyway, I've never had exposure from an edge leak like that go far enough to effect an image.