Yeah well, oats and oat bran may have a fairly high GI rating, but they also have actives like Beta Glucan that lowers blood sugar. I've known a couple of people who've tested BG levels after eating oat bran in particular and their BG levels DROPPED from fasting levels after eating raw oat bran, and the effect lasted.
It's not as simple as just GI, obviously. There are reasons why oats and oat bran are concidered somewhat anabolic.