You..... just made my day.
I personally detest these fluid fill procedures that require exacting temperatures. It's such a scientific requirement that can't be replicated by normal people maintaining there cars.If you heat 6 quarts of ATF up to 150 degrees on the stove and measure the volume, and then bump it up to 200 degrees and remeasure.. the volume is prolly' within a 1% difference.
Regarding fluid level, the insides of a transmission is a very dynamic place. G loads from acceleration , braking, cornering and bumps has the fluid sloshing all over the place.
You should try to get the level spot on... but if you dont, I doubt its really a concern.
There is no "Hot Check" at the GM factory. They build the tranny, dump in the fluid.... and roll.