2GR-FKS 2021 ES 350 auto tranny fluid service

[Natty Bumppo]

I realize there are many posts and discussions here on doing this with the sealed tranny and the great details of gravity draining and refill and the explanation about the correct warmup temp to set the fluid level. All great info however I have a question.

Assuming the tranny was correctly previously filled at the factory and never serviced, no leaks and thus at the correct level and car set up level.  And also not discussing if service should be done based on mileage and years.   Why not service this later model auto tranny when is fluid cold from over night set up on stands with over night cool down of fluid, then accurately measure the volume of gravity fluid drained with stand pipe removed, then replace standpipe and drain plug and refill with the same volume of fluid at the same cold temp of drained fluid (new fluid containers stored in same area as car)?  And forget adding extra fluid then warmup to factory temp spec range and pull the drain plug and drain to a trickle.    

Thank you 

Pete