nobody talks about it because everyone is following IIFYM and that sort of bs type of eating
yes glycemic index and load are huge differences, so much so it can make the difference between dying if you are a diabetic.
example the glycemic index of a bagel vs. watermelon ARE THE SAME
yet the LOAD of the two are drastically different. this is another reason why counting calories is a load of bullshit. the bagel and the watermelon have completely different partitioning effects on the body.