This spot on ..I think this all started when people started adding these sugary drinks...pre ..inntra...post ..when they take skin. That's just a bunch of shit calories.
If I'm eating 300 carbs of real food per day, and I want to take 10iu of slin, it makes sense to make sure I have 100g carbs pre and a good dose after. These 100 or so carbs I pull from my existing 300. Sure I can have some shit carbs (for me smarties I don't need a dextrose shake to carry to the gym) in my bag. But if I happen to go hypo and take 30g of carbs at the gym, subtract them from a meal later in the day.
This is my approach. The more slin the more of my daily carb intake is consumed during the window.