Iodine is an oxidant. As such it could function as a bleach and form an Iodide salt of Silver metal. However, betadine is rendered very weak for application to human skin. I have never heard of it being used as a successful bleach.
I suspect no, or very little bleaching is taking place in spite of the post. After all, there is no proof one way or the other as the post lacks any reference. OTOH, the Betadine may be oxidizing leuco dye which might be otherwise colorless. IDK. All speculation until all of the checks and balances are properly presented.
This was a single stimulus experiment which gives us an open ended result from which no conclusion can be drawn. Please remember that. I stand in bewildered awe at the number of people who accept a statement with no proof one way or another in this regard.