Ah yes, this old favorite. It’s no contradiction to what @Thas and @YogaO said to note that my favorite response to this was recently posted on another thread:
Bernstein has written about his law of small numbers. It basically says that fewer carbs drives taking less insulin which in turn means smaller mistakes.
This, to me, is the voice of someone who has actually experienced living with this disease. Some people do find “Eat what you want and dose for it” to be simple, followable advice, but a LOT of us find we need to rein that in considerably to avoid riding the BG roller coaster all over the place. In my case I restrict most of my carbs to midday meals (chiefly bread, because sandwiches are just so darned convenient compared to everything else) and keep it low-carb or no-carb in the evening because it’s just so darned hard to hit the carb-insulin number exactly on the nose, and then I find myself waking up the next morning with a higher fasting # than I like to see, or worse, risking an overnight low that at best is going to force me out of a sound sleep to gobble glucose tabs and at worst… well, we all know what at worst is.
To me it’s just a lot easier to Not Go There. Possibly because I had 20 years on the old R/N thing where there was a lot more Thou Shalt NOT and “eat what you want and dose for it” wasn’t possible, let alone recommended. Looooonnnng experience of just keeping my hands in my lap when the pastry plate comes around during weekly staff meetings and the like.