Transmission fluid drain & refill procedure

Like many of you were a Toyota family. In addition to my ‘21 Tundra, my wife has a ‘14 Sienna Limited AWD and kids share a ‘13 Venza Limited AWD. I’m generally aware of the Toyota procedure for transmission drain & fill.
108 degrees, etc.
Assuming, for example, I drain exactly 3 qts of transmission fluid out at 70 degrees and add back exactly 3 new qts also at 70 degrees (garage temperature). Wouldn’t this be the correct amount? Exact amount in, exact amount out at same temperatures. I don’t see how you could underfill or overfill using that procedure. Thoughts?

 

Millions of threads on this. But yes. Put back what you take out. Don't complicate your life.

 

You could star with less in the trans than recommended. Then drain out 3qts and put back in 3qts and still be low on fluid. The only way to ensure the proper fluid level is to follow the procedure in the FSM. Lots of threads in here describing it.