I can not argue traction because i have no way to measure it. My physics instructor always said I could have a coefficient of friction greater than 1 and that always baffled me.
I think it is more related to under steer vs over steer. The general rule being that as you lower pressure the tire tends to move toward under steer and as you add pressure it tends to move towards over steer. The problem is where is neutral. I think at 20 the tire is just starting to have some under steer or less over steer to the point that i can perceive it. Now if increasing under steer increases traction I do not know.
I think it is more related to under steer vs over steer. The general rule being that as you lower pressure the tire tends to move toward under steer and as you add pressure it tends to move towards over steer. The problem is where is neutral. I think at 20 the tire is just starting to have some under steer or less over steer to the point that i can perceive it. Now if increasing under steer increases traction I do not know.