A very thorough and partially incomprehensible, to me, explanation but I trust em. Even though the sound is evident without "bouncing" it's much more audible than the stock shocks ever were.
Bouncing on the bike in a "garage test" creates an unrealistic, low velocity impact on the shocks. Viewing your video, it would appear that he noise you hear is the piston valving. This is caused when bouncing on the bike when the bike is not in motion, which causes the three individual compression valves in the piston to be slightly opened and the check ball controlling oil flow, which is backed with a valve spring, is barely unseated and bounces on the minute ridges created during machining of the valve seat, which then causes a chirping/honking sound. This noise will not occur when you ride the bike in real world motion. The chirping noise will also decrease over time in a "garage testing" situation as the check balls wear into the newly machined valve seats. At zero mph you may also have some sound related to the spring guide between the two springs and the body of the the shock. Again, this should not be perceptable when the bike is being ridden.
Whomever said all good things in moderation certainly never rode a bad ass Bonneville