Here is the explanation I got from a well experience Dyno Tech, Just for info.
"The deal with what gear to run was started in 4th gear when the evo's were around and stock, they could not pull 5th (1:1) gear, and the touring bikes would go faster in 4th than 5th.
When the TC came out with more torque, it could pull 5th. So 5th (1:1) was correct, until the 6 speed direct drive (1:1) came along.Now, if the engine has enough torque to pull the overall higher ratio but still in 1:1, that becomes the gear to use, however if the engine is bone stock, 6th is usually too tall for the same reason that the evo 5th was to tall. All tuners are doing is trying to tune using the gear with the least loss through the transmission, whether it's 5th or 6th. Which ever is the direct drive of 1:1. Power readings recorded in fifth gear are usually higher than those in fourth due to loss of power transfer in the gear box." Wood cams power readings are done in 6th.
Take it for what you want???