you're referring to the glycemic index and how oats are a very low glycemic food and sugary foods are very high. the view that glycemic index has any real effect on digestion has apparently been debunked
Glycemic Index Setting The Record Straight - YouTube
Layne Norton also did a video explaining it. the studies that pointed to glycemic index being important required participants to eat nothing but carbs on an empty stomach. so yes, probably if the only substance in your stomach is a sugary food, it will burn fast and store fast. but if you eat sugary foods and your stomach already has other stuff in it, the fact that it's a high glycemic food becomes meaningless
. it will be digested slowly because it's affected by the digestion rate of the other foods.
you speak so confidently and with such authority about complex processes that aren't fully understood by a lot of people. you can't blindly trust everything you read on the internet, and i certainly think it's a bad idea to plan your diet around your own personal conception of "insulin spike."
can you answer these questions?
1. how much does whey raise insulin?
2. how much do carbs raise insulin?
3. what is the exact process by which muscle glycogen stores are replenished?
4. exactly how much of a rise in insulin is appropriate for my
body post-workout (seeing how everyone's needs are different and you can't generalize)?
if you can't answer these questions about the statement you just made, then it's bro science and it will not be useful to you in any practical way
. try to read more critically and be more skeptical about what we actually know for undisputed facts about the human body. the same goes for the things you read about supplements. trust your own honest experience over anything you read on the internet, not the other way around.