I'm not an expert but I think there's a difference between "Nock to Nock" and "Tip to Tip" being exactly what you're trying to say.. I think Nock to Nock is measured with the reflex already and Tip to Tip is measured before reflex is added (the actual piece of wood you're using at first)
Correct me if I'm wrong folks, I'm here to learn aswell 😉