Playing devil's advocate here: technically they
can drop faster than 9.8m/s^2. If their head is down they can use the inertial mass of their neck/head as leverage to drop when they raise their heads while they're preloading their legs/body. It's been documented on growingdeer.tv:
However I would imagine its a finite offset since they can only move their body "so much". Also a lot of that "vertical" movement is lost to wheeling/turning as
@kyler1945 has stated.
The chart is interesting but only takes into account a single dimension of a much more complex multi-dimensional problem. However as humans we like things to be dumbed down and simplified into a single scalar metric. Take from that what you will, I'll continue to shoot my slower heavier arrows because the results have been good for me thus far.