Motor windings are downstream of bus capacitors and therefore not an influence here. The cables and bars are the inductance of concern in this situation. It doesn't take much inductance at high currents to cause issues. That said, during normal use the electronics will stop drawing current before turning off the contactors and so no arcing happens then. It's only in the safety shutdown case that breaking the arc is an issue.
My understanding is that capacitance across the contacts would be undesirable for safety concerns since they can carry AC currents. It is reassuring how Tesla isolates the pack so well when the contactors are off.