This makes sense to me, but I am not LADA. if your total insulin per day varies from 20-30 units, taking 10 by injection (long acting, once/day), means your pancreas only needs to provide 10-20, and can adapt timing to when you need it. May allow you to be less restrictive in your diet.
Why do you think diet control is better for you ?
Can you ask your doctor for studies or research supporting early use of insulin? I think there have been discussions here about that.