A high-pin is a physical position, not a procedure. Simply means the recess in the pin is too high for the jaws to engage it. I suspect a pin on top of the jaws is less common that what we had here, where the pin was just slightly too high.
Anyway, I also appreciated this last installment of the video, and I'm happy to see that they got a good handle on what they did wrong. And also give them props for not blaming the hitch, but accepting responsibility for their mistake. Basically it is 99.9% never the fault of the hitch, regardless of what brand or design. My opinion is that particular hitch is more complicated than it should be.