Quick...You have way too much time on your hands.....

You need to realize that the term jumping the string is a very old saying...
I started bow hunting in the early 70s, before compounds, and the term was around at that time....It's easy to say they are ducking now, because we have so many videos on TV...When the term was coined this wasn't so.

My bow isn't very fast.........But it is real quiet....That and taking a shot at an unsuspecting deer are what helps keep them from ducking the shot.....

btw....I don't think they even know what they are doing, they just hear a strange noise and crouch before they leap....Its more of a reaction...