Not arguing, but are you crazy? This is really about inline with people draining there engine oil at like 5K miles or below without anything to support there process.
Why would you drain that soon and so little? Unless you are doing longer drain like myself, you are wasting money here along with resources and time. Put in Amsoil go 25K and the fluid will last 2 to 3 times that. I have used Amsoil in trannys that are prone to rebuilds and after 50K miles on the fluid it was like new (color and smell).
I would never flush but drain and fill, yes. Without draining your TBN will still be low and TAN much higher. Nevermind the OXD and NOX in there. Nor higher then "drain" wear #'s. That is like draining your coolant reservoir and never draining the complete rad…
Toyota fluids are over pimped, over priced fluid and not worth $%^&.
I used Castrol domestic car Transmission fluid which meets Dex-III requirements.
Every 15,000 drain and refill.
next 15,000 i takes to mechanic, who replace filter and refill with my fluid.
Presently I have 297,750 miles and runs like new car.