I finally figured out why PSCN conducts to NSCN even though it's vice versa in real life.  Turns out that while electrons flow from N-type to P-type in real life, electric current flows opposite to electron flow; SPRK simulates electric current, not electron flow.  When SPRK travels from PSCN to NSCN, you can imagine an invisible electron moving from NSCN to PSCN.  So PSCN conducting to NSCN is actually realistic.