Nor mine - but it's one of my favourite spices, and I've used it for most of my cooking life, from well before I was ever diabetic. It's actually a blood thinner which might possibly account for reduction in glucose levels?
Whether it is rubbish or not cinnamon is delicious with some berries on yoghurt either as a dessert or for breakfast. Try it. What works for one person does not always work for another.
My understanding is that it is only Ceylon cinnamon that seems to have a positive effect on blood sugars, which the majority of cinnamon is not! It is a lovely spice to be sure, so enjoy! Cheers/L