Ann: Annual General Meeting Presentation, page-80

Buy back 80% to take the share off the market and reduce dilution (by a tiny fraction), buy back at same value they were "sold" at and the washout will result in nil adjustment.
We never had the money from the "sale" so we dont need them on the market.
The holders need to cough up the cash for the balance so they have actual skin in the game and so they can feel a bit of pain like the rest of us.
Forcing them to pay the loan in its entirety would be counter productive in this instance.