Are you referring to the Expedition Unknown segment that aired in January 2017? If so, the Washington state portions of that segment were filmed in August 2016. At least three posters on this site were also in that segment. I don't remember anyone named Hall being in the segment or a discussion of the stairs being capable of being deployed from the cockpit.
Eric Ulis, who was not in that segment, has a Facebook page that Josh Gates also belongs to and he has appeared in cable programs with Gates. Anyone reading this who also belongs to that Facebook page could ask Gates if he knows anything about Halls' claim.
EDIT:
I am not sure if he was actually on the show, I forget the details of the last segment, it sounds like he may have been. But I guess his theory that the hijacker jumped on the approach to Reno was what was covered at the end of the episode. If you go to this link, this is what seems to indicate, he was more of an off camera consultant:
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I have read the Hall article linked above and, as you can probably easily guess, have a number of problems with it.
His discussion of the parachute that Cooper selected is wrong since both backpack parachutes that Cooper had access to on the airliner were surplus military parachutes. There were no "civilian" parachutes involved and FlyJack and others have explained this in detail over the years.
His description of what is now known as the Western Flight Path is completely wrong. No one has ever claimed that the airliner flew 20 miles to the west of the Victor 23 airway. There are other problems with his flight path analysis and why the airliner headed to Reno to refuel.
Hall suggests that Cooper planted the money found at Tena Bar seven years after the hijacking. I honestly cannot believe such a claim. After getting away with the hijacking for seven years, why would Cooper bury about $6000 at Tena Bar and which would only later be found by accident? Dream on!
Josh Gates about to "throw up" before making a tandem parachute jump? I don't believe that either. Gates usually included a segment in his Expedition Unknown videos of him dangling from a cliff, sliding on a cable across a deep canyon or some such thing, or doing something underwater that I definitely wouldn't do. Gates diving skills may have been genetic as I understand that his father, or maybe grandfather, was a professional hard hat diver. But basically, Gates was/is an adrenaline junkie.