Ill the experts give you the right answer.
My guess is two fold:
the point is that chametz needs to be burned.
First off when the hebrew slaves were getting to leave it didn't take an instant to leave. They had to prepare to leave. So that time of preparation I doubt they were munching in bread.
Secondly, it takes several hours for chametz in our digestive system to get digested. Hence you don't ready bread 1 hr before pesach.
I know it's a long shot..... Chag sameach