The problem is not the presumption of the FRB not redeeming the notes. The issue is the assumption the redemption is for gold. The definitions of words have been shifted, per above, to identify redemption into another species can occur or may not even be required as the notes are 'lawful money'.
If he is pursuing the PAG angle, good on him. Hope he knows enough to put certificates into the evidence jacket.
IMO, I think it is fruitless.