Controls whether this shape produces pre-contact and pre-continuous callbacks. This only applies to Dynamic bodies and is ignored for triggers. These are relatively expensive so disabling them can provide a significant performance benefit.
A pre-contact callback calls the PhysicsShape.callbackTarget if it implements IPreContactCallback, and a pre-continuous callback if it implements IPreContinuousCallback. The deprecated Unity.U2D.Physics.PhysicsCallbacks.IPreSolveCallback is also driven by this switch, for targets that only implement it.