You don't think pressure matters when plunging? I've speculated that a faster plunge might extract more solutes from the coffee grinds due to greater liquid penetration into the coffee grounds from higher pressure.
It's hard to get that much pressure variation with an aeropress. The plunger is around 5 cm x 5 cm, so the full body weight of a male human (say 90 kg) only gives you 3.5 bar. That's if you're standing on your aeropress. A real espresso machine puts out 9 bar.
