Without having watched the video, a jammed rudder can be a very serious emergency, depending on how far over it is jammed. That said, a reasonably safe landing should be possible with a hardover rudder if you pick a big, wide runway and land going fast enough that you can maintain directional control via the ailerons against the rudder to touchdown. Landing with a crosswind from the side to which the rudder is cocked will also make things easier -- the more crosswind, the better. Of course, after that, it's liable to be Mr. Toad's Wild Ride, especially if the nosewheel is hardover along with the rudder, and you're probably going to at least groundloop it in a taildragger.
And now that I've watched it, they're talking about just not using their feet during flight and leaving the rudder neutral. Based on my instructing experience, thousands of pilots fly their planes like that every day without serious result (even if it is a pretty sloppy way to fly).
And while you can use the doors to provide some yaw control if, say, the rudder cable breaks, there's no real need for that unless your only choice is to land on a narrow runway with a howling crosswind.
