From the quick googling I did at work, it seems that there are different types of starches that digest at different rates. Whole grain cereals are in the slower-to-digest category *and might not get digested fully.
I personally suspect that the process of making oat milk - blending and straining the oats - makes them easier to digest and probably has an impact on GI. So it's probably a wash.
If someone else has to debug the problems caused by a parent naming their child with a special character, does that make the parent the bugger? 🤔