When the only tool in the box is a hammer...

Everything that needs fixing looks like a nail.

What are the action and reaction forces when a hammer hits a nail?

Diabetics are issued with blood glucose meters - and nothing else.

For people with type 1 diabetes, that's fine. They lack insulin, so they have to inject insulin in the right amounts & types to keep their blood glucose levels within reasonable limits. Applying Bernstein's Law of small numbers by reducing carbohydrate intake to a minimum keeps blood glucose levels within reasonable limits (between 3 & 7mmol/L) most of the time.

For people with type 2 diabetes and a fat belly (~85% of type 2 diabetics), that's not fine. Their disease is a disease of excess, causing dyseverythingaemia (hyperglycaemia, hypercholesterolaemia, hypoHDL-cholesterolaemia, hyperNEFAaemia, hypertriglyceridaemia, hyperuricaemia, etc). However, because the only tool in their box is a blood glucose meter, their disease looks like a disease of high blood glucose level (hyperglycaemia) only. Applying Bernstein's Law of small numbers by reducing carbohydrate intake to a minimum keeps blood glucose levels within reasonable limits, but makes everything else worse if energy from carbohydrates is replaced by energy from fats.

EDITED to include information in the comments: Only if energy from carbohydrates is reduced to a minimum AND energy from fats isn't increased to compensate (i.e. eat a PSMF or a Modified PSMF), does carbohydrate restriction help people with type 2 diabetes.