[SCHMIDTY]

Regulators have diodes that prevent reverse current. A simple diode test is to connect the B+ wire to the positive battery terminal and ground the regulator case then use a test light and touch the connector pins, should not light the test light.

 

[SCHMIDTY]

Also the reversed connector doesn't make sense. The stator isn't polarity sensitive nor is the regulator !
How did the OP figure out the stator connector was wired backwards ? Single phase or 3 phase doesn't matter.
OR am I confused ???

 

[SCHMIDTY]

My bad, I mistook that the stator to regulator plug was backwards.
The regulators can still be tested with the test light and by plugging them in and check for volts at the battery with the engine running.