Hello!
We've logged this issue as a feature request, currently Rigidbody does not support enabling and disabling via script, unless the whole GameObject is disabled.
Another thing to clarify is that turning a Rigidbody component kinematic does not mean, it does not participate in the simulation step. Kinematic for rigids simply refers to the object being immovable (infinite mass). At the moment a limitation of our integration with PhysX is that we keep reading back the position and rotation of such bodies each simulation step.