I am going to agree with you that following a proper diet will help regulate your numbers even for Type I diabetes. However constant testing must be done to know what your numbers are as odd things can raise your numbers. My grandson is Type I and his numbers can fluctuate wildly from fruit, especially bananas. He is supposed to eat fruit- and being a growing boy he is supposed to eat a balanced diet to include more carbs than recommended for adults. His insulin has to be adjusted from meal to meal in order to know how much insulin he needs. I do NOT recommend that people stop testing or decrease testing. My grandson was not diagnosed until he was in a coma- I sure don’t want to ever go through that again.
Eating fruit in any significant quantity, and any processed carbs at all, is a huge mistake for any diabetic, and especially for a type 1.