It is possible for most people to do a one arm chin (at least one) if training for it. Problem is that this movement can be a ego buster. And because you will usually fail at first. Just like any other lift, it should be approached with serious intent , with a planned workout scheme. If your greatly overweight, and not that well trained,than the one arm version may not be for you. The average well muscled and strong BB'er should have no problem learning his movement. You can't get good at anything unless you try it. You might even surprise yourself.
Try doing normal chins, at first, in a chinning workout. Than switch to the negative portion (should be warmup'ed enough)this is where the confidence can increase along with the muscle impulse action/reactions. The Rest/Pause system works well here, giving 12 to 15 seconds between negative attempts. Or alternate each arm, with that 12-15 pause between. Or find a way that suits you the best. Should become stronger each workout.
I have maxed at 3 reps one arm chins, at around 235-240 bwt. In college, at 275-280 (football bwt), I did the normal two hand chin with an extra 120 strapped on, counting the chain and harness (if I remember correctly). My chinning efforts, either one or two hand, are like the guy in the video. Giving a slight break, at the elbow, so never from a dead hang start. Any of these chins are not "all that", just something I, and others, have done. At present, my two hand chin has improved very well, at a lower bwt, since college.
Art Jones mfc makes quite a bit of medical and rehab equipment, more than just BB'ing stuff. Ever go to a rehab/VA center, there are devices that most have never heard. From Art Jones, among others.
Not sure why some get their kilts in a knot and over react to the positive/negative one arm chin. It's just another lift, that most strongmen like doing. Good Luck.