I am not sure if mine is a just a simpler way to look at it as well as not as technical...but I do not believe that there is any balls that the mass bias is not on the intermediate axis.
In a symmetrical core ball, the low RG is the X axis and the high RG is the Y axis....in asymmetrical core balls, the Z axis is the intermediate.
The way the dynamics of the core are changed is by drilling into them. In a symmetrical core ball, drilling anywhere along the high RG plane or Y axis which is 6 3/4" from the primary pin or low RG axis, creates the strongest amount of asymmetry, the larger or deeper the hole the more it affects the dynamics.
If there is a certain amount of asymmetry created by the Z axis, you are creating asymmetry one way or another. You either are using an oblong core, one that has the low RG or X axis, the wider portion would be the Y axis and the narrower portion is the Z axis. Drilling into the Z axis reshaping the core increases the asymmetry. If you use a symmetrical core ball and add a denser piece to create the Z axis or a mass bias, drilling into this mass lowers the asymmetry by reshaping closer to a symmetrical core ball.
The views and opinions expressed by myself are solely those of mine and NO one else, nor are they affiliated with anyone else.