I admit, this really gets tiring, and I'm about at my limit. So let me wind this up.
Neither the U of M quote that you sent nor the link, which was to a document selling some nutritional formulas, says that Vitamin C is a mercury chelator. I actually took the trouble to look through it.
If your office believes that Vitamin C binds with mercury and carries it, then I would assume they tell patients with mercury toxicity not to take Vitamin C prior to Amalgam removal. Is that true? If it is, then it is terrible advice.