I have degrees in chemistry which is why I questioned the exposure to sulfite after development. From a purely chemical perspective the stain once formed is insoluble and hard to remove. It will only dissolve in concentrated solutions of sodium or potassium hydroxide. I doubt that sulfite ion is a strong enough reducing agent to bleach the stain.
Unfortunately there seems to be little scientific study of staining developers. What I have found on the internet is mostly conjecture and personal bias. There is also a lot of bad information and even mysticism. One example, the need to place the negatives back into an alkaline solution after fixing.