On the link you provided, seems to me if the liquidation preference of the SPS keeps growing and the SPS is not cancelled, the legally available assets for distribution will not be enough to distribute to stockholders both JPS and common. All monies go to the Treasury. This will wipe out both common and the JPS?
"In the event the assets legally available for distribution to stockholders are insufficient to pay the liquidation preference of all Preferred Stock in full, the assets available for distribution will be divided among all holders of Preferred Stock on a pro rata basis, based on the value of the liquidation preference of each series of Preferred Stock." Page 5
More details about the conversion offer are on this overview sheet, which clearly lists the Series AA ("public preferred stock") as one of the series to be exchanged.
To connect the dots, the Series AA preferred shares got converted to common even though their contract said they don't have conversion rights.
That language clearly didn't prevent Citi from offering a conversion. That means the analogous FnF situation is exactly the same: FHFA (with all common voting rights it succeeded to as conservator) CAN offer the juniors a conversion to common, even though the juniors' contracts say they have no conversion rights. Which means you're wrong yet again.