GFCI and an Open Ground

BB_TX wrote:

But the description describes a "grounded neutral" which goes back to the question of how can you have a "grounded neutral" when there is no ground connection at all to the trailer. Current does not flow into an open ended wire. And an ungrounded frame is effectively an open ended conductor.

For current flow, there can't be a grounded neutral when there's no ground connection. That's what prompted my speculation a bunch of posts ago that if the shore cord's ground pin is not connected, downstream neutral-ground fault detection will be lost.