Sorry, I thought of something else to add - if you couldn't tell, this hits close to home to me.
Even if your grandson ate NO carbs, he would still need baseline insulin because his body makes none. Since he pumps, his pump is constantly delivering insulin into his body. If he were on daily injections, he would take a basal insulin to act in the background and then bolus with a fast acting insulin to cover his meals.
I often wish Type 1 and Type 2 diabetes had very different names, because I think that would help to clear up the common misconceptions about the diseases. They are not as similar as one would think, and the media constantly refers to diabetes, meaning Type 2 in I'd say 95% of the cases.