Dude, you just said you buy your beef directly from the farmer and you quibble over oat flour
That was just a suggestion.
You can't get a flour consitency with a food processor so the idea behind the flour is it won't be as gritty thus more palatable. It takes a whole lot of reducing to get a flour and a blade alone is not cabable of that kind of size reduction.
The GI change is negligible and it really doesn't matter if a person has already had a pre-workout shake or a meal not to far back. It would hardly make a difference in the long term whether person had a bowl of oatmeal or a shake with oatmeal post-workout.
The reason Pity and I suggest a shake is if you don't like oatmeal regular.