There are several ways a high pin can close the hitch jaws...on any hitch.
The you tube shows the trailer looks like it was set where both plates (hitch plate and pin box plate) were about the same height. Then for some reason the actual hooking up was edited out of the vid. There is way too much gap showing between the plats....and the gap will not add up to the jaw thickness when we look at a actual high pin.
This is a typical hitch attempt when the trailer is set to high. The flange on the bottom of the pin slides over the top of the hitch jaws and touches just enough close any hitch jaws. Keep in mind the hitch plate has a bit of tilt which allows the pin flange to trigger the jaws to close. When the trailer is lowered on the hitch their isn't the same amount of gap all around. Usually the gap is bigger in the rear however in the vid the bigger gap is on one side which says a possible high pin or the nylon slip plates are waded up on one side.
I've seen this around truck terminals and loading yards which is the #1 reason for a high pin on flat parking surfaces. Scenarios change when parking surface are not flat side to side between the truck and trailer. We see this a lot around construction work sites.
The you tube'r may know what he did or didn't do...or like many RVers in the past on this website and other rv forums have said they never found out what went down. Maybe his next vid can shed some light on his thoughts or his findings.