I'm going to theorize a little....
If, by demonstration, he IS producing just HH with electrolysis, (and not chemical redox)
we logically have to deduce that the cathode is busy producing HH while the anode is being inhibited / prevented from producing O.

I think he stumbled onto something in trying different metal electrodes and electrolytes
to see what would happen and observing the effect.

Take for example,
In the Ravi/Lawton/Meyers design..... it became an observed phenomenon that a white "coating" would develop on the anode side of the stainless steel tube design.  It was determined that this was beneficial so people started experimenting to enhance and expedite the effect and it then became common to "condition" the tubes for better production.  Some questions should be asked.

Why / How did this "dielectric" , non-conductive, coating enhance production?
Production of what?  Were you still producing the same ratio of O to H?
What if you used "other" metals for the anode? What kind of coating would that create?
Are you still ionizing (charging) the water with the same ratio of ionization (+) (-) ?
What if an accumulated resident (+) charge of the water itself starts to replace a "coated" anode?
Is the chloride ion even necessary? If so, what "coating" is it creating? On what metal?
Could a normally "sacrificing" metal become coated so as to prevent/inhibit its decay?

OK, when they talk about plate conditioning, they are referring to the oxidation of the chromium in the stainless steel cells/electrodes. When plates are properly conditioned, the accumulation of brown sludge at the bottom of the cell diminishes to very little/almost nothing. But that takes a little while. Coatings as you refer to are typically on the positive electrode in the form of an oxide (but not written in stone).
They prevent the oxidation of the steel in the stainless steel from absorbing oxygen, thus increasing cell efficiency and oxygen production.

Chlorine isn't needed nor wanted. It reacts with just about everything in a bad way. See http://en.wikipedia.org/wiki/Chlorine

About the sacrificial metal. You refer to noble metals. Aluminum is one of the most reactive (sacrificial) metals. If you want to run a lawnmower off of Hydrogen, you would use aluminum shavings or slivers in a sealed container (with one small opening to extract the hydrogen) and add a strong alkali to the water. As the aluminum oxidizes, it gives off a lot of heat, and the hydrogen gas. If the aluminum is too thick, it can oxidize over and production can be reduced.

If you want to make an electrically controlled hydroxy cell, the general consensus is to use all stainless steel, preferably 316L grade.

I have been experimenting with the use of copper for the negative electrode and stainless for the positive, since copper is MANY times more conductive than stainless. And it is a terrific conductor of heat. Excellent for heat control if used as a tube instead of a plate.

To preserve the copper, I may stick with baking soda, because a strong alkali could disintegrate the copper.

Copper as a positive electrode disintegrates VERY rapidly.

The absolute best electrodes are made from platinum, but who can afford it?