Rotary train car coal dumping - GIF and video

[mklotz]

I'm still puzzled about what happens at the couplers that link the car-to-be-tipped with its adjacent, non-tipping car(s). In the first gif, I don't see any car movement that might suggest the cars are being un-coupled prior to tipping.

Are the couplers on these cars mounted such that they can rotate about a horizontal axis to allow the tipping without uncoupling?