To say that Safe Harbor assets are under the jurisdiction of the bankruptcy process (fully) is too broad a statement in that there are restrictions to it's applicability.
Under normal circumstance if there were say $50B in SH assets that were returned, Preferred would be paid $7.5B + interest and the rest would belong to Commons.
This scenario we know does not apply because APR was "consensually violated" so that Commons could participate and receive a distribution simultaneously with Preferred.
Once there are actually Debtor owned Safe Harbor assets available they will be distributed according to the POR by default since it is the only document that can be utilized.
Preferred holders, particularly TPS, could not be expected to allow the lower priority Commons to receive payment on par with them, only to later decide that APR is now applicable.
The process simply does not work that way, Commons sacrificed their "estate ownership rights" and control of legacy assets for an opportunity to survive the bankruptcy process.
SERIES-R PROSPECTUS
Liquidation Rights....pg S-6
Upon our voluntary or involuntary liquidation, dissolution or winding-up, holders of Series R Preferred Stock will be entitled to receive out of our assets that are legally available for distribution to stockholders, before any distribution is made to holders of our common stock or other junior securities, a liquidating distribution in the amount of $1,000 per share of Series R Preferred Stock plus any declared and unpaid dividends, without accumulation of any undeclared dividends.