Yes, what you say is true. But remember, the stock was deemed worthless, to WMI, because of the TAKING of WMB. Now that has nothing to do with the damages caused by the FDIC that was outlined in that footnote. It was termed a "TAKING", and CONVERTED, meaning effectively, STOLEN. Also, violated the 5th amendment I believe. This is the point that seems ambiguous to me.
REmember, WMI had already downstreamed big money to WMB, and they never got it back, so that alone makes WMI a creditor, no?