I was looking at "flip" as a possible - I understand "flip" as being induced by the air immediately behind the pellet when it's released from the barrel.
The blast of air immediately behind the skirt catching up with it? If the only air is behind it, theoretically the pellet is beyond influence.
A tighter fit of the pellet to the bore should have less turbulent air passing by as it exits from the barrel and thus influencing it's flight less when compared to a looser fitting pellet as more air has passed by causing a more turbulent atmosphere around it as it leaves the bore?
Would the lower air turbulence on exit of the barrel have that greater effect?
Just theorizing, but beginning to lean towards the "softer" pellet base.