The bow down attitude is the result of restrictions in the angle of the rudder foils and the different speeds upwind vs. downwind.
Upwind, the boats are relatively level; the boats are moving 25-30 kts. A higher angle of attack is required on the rudder foils to lift and stabilize the back of the boat.
Downwind, the speed increases to 35-40 kts; a lower angle of attack on the rudder foils is required to achieve the same lift, so the boats assume a bow-down attitude.
I do realize that's what Oracle said about their bow down...but it also stands to reason that they would want to rake their rigs more vertically when sailing downwind and rake them back upwind...all I'm sayin. There is no advantage for everyone to spill their techniques - trust nothing any team says at this stage
