Some wild guy in Vegas mentioned to me that attaching a magnet to a large piece of steel spreads out one of the poles so it is no longer a focused, concentrated field. Which apparently turns out to be the same thing as magnetic shielding. The pole is still there, but so spread out you can hardly detect it.
Then we also learned from SuperMagnetMan
if you quash one pole, effectively the other pole goes away too.
So to get imbalance it's really a matter of field density--focus one pole while dispersing it's opposite pole.
In the case of the Earth Engine, it looks to me like you want the two magnets to have widely dispersed fields when they approach each other and as they cross, then you want highly focused fields of like poles to create strong repulsion. Still not real certain about the triggering Dennis uses, but I suspect it pushes the two magnets past the "sticky section" and apparently it requires only a small fraction of input energy compared to the total torque generated from the repulsion.