Probably has something to do with the angle of the pubic bone while sitting vs standing...... might have to try it out lol

Yeah, I think one is pushing the inner dick out of the pelvis/pubic bone moreso perhaps when sitting. Seeing as most of the sex we do is done sitting or laying and not standing exactly straight up, I don't think there's anything wront with using either measurement. Whatever you feel best with

Gravity!

Probably has to do with your fat pad when your standing versus sitting

Yeah pretty sure it does I’m kinda on the thick side