I’m considering the clarified question:
I was considering it a question about the pressure changes on the portion facing down vs those upwards.
My understanding of the physics of drafting was what I was considering. Not sure why that is hard to understand?
@TriPolar I guess then my understanding of the physics of drafting has been wrong?
I understood that lower pressure forms behind the lead cyclist dragging on them. A cyclist behind them benefits by being in that lower pressure zone and to a lesser degree benefits the lead rider by reducing the the drag on them. Someone in the middle of a larger peloton gains the most benefit.
That effect, however I may be misunderstanding it, is big enough for me to be able to notice even at the speeds I was able to hit.