That is terrible advice. Vitamin C is a chelator of copper. Lowering copper lowers the body's sodium to potassium ratio - a key vitality indicator in the body. If the sodium to potassium ratio is high, then there maybe a short term positive effect to taking extra Vitamin C. However, you would only know that by doing a HTMA, and if you did that you would get a much better whole body approach to bringing the body back into balance.
I personally took lots of Vitamin C (and B-5) per the recommendation of Dr Lam for treating adrenal fatigue. Felt better for the first 6 months, then crashed and never recovered. I kept at his approach for awhile trying to turn my health around - ended up so tired I could barely function. That's the downside to taking the wrong supplement, the wrong approach.