I have a hard time believing you can measure by volume precisely enough to see a humidity driven difference.
Personally, I don't think humidity makes enough difference that you need to account for it.
Ok. I don't need to measure by volume that precisely, I just use the same sample.
It's something I did many years ago. I measured a cup of flour from the refrigerator and left it out all day on a humid day.
It weighed more at the end of the day.
So is my hydration calculation accounting for the water already in the flour?
I suspect you are correct and it's not enough to matter. Then for someone who is consistent with their volume measurements it shouldn't matter either.
Just posing a question of interest.