Not known Details About 230 to 12 volt transformer
If your three-prongs are angled as a way to have the ability to be plugged right into a three-prong 50A receptacle then you are accurate in that it would need to have a built-in jumper and the 120V neutral & floor could be tapped off precisely the same wire. I do not see how the solution might have acquired its CSA listing if that was the case. I