?? Beats me.
Maybe they have a tower up in a forest, at 20 feet, and measure winds there?
The winds at 20 feet would be less than 100 feet up, especially if within the canopy of trees.
I imagine winds at 20 feet are a lot less than the clean unobstructed winds at 100 feet up.
Then again, maybe the typist of the report was just wasted.