Joe,
If that were the case, I doubt we would ever get an arrow off the string cleanly. One of the big culprits in bad tuning is nocks that are too tight. They hold on to the string too long and cause all kinds of havoc.
The arrow should leave the string as soon as it's own velocity exceeds that of the string.
Tedd,
Can't be. That energy already had the opportunity to transfer to the arrow. Whether the string stretches as a result of energy left or not is irrelevant.
Put another way, whether you stretch the string or pound the nocks with that energy, it still ain"t going into the arrow.