The only time keto works for diabetes is when it's low calories, any low calorie approach can be beneficial short term for diabetes management. The only approach that reverses diabetes type 2 without unhealthy restriction is a whole foods high carbs approach. This is because higher fat diets literally coat your cells with fat which in turn makes it harder for carbs to make it into the cells, this means the same amount of insulin can't do it's job to varying degrees, prediabetes / diabetes.
I'm not a fan of low carb, but I do know some people who are plant based and low carb and they say it works for them.