Our position is firmly that contracts must be executed entirely as they are, and that no claim can be diminished post default, but only increased (and preferably significantly).
That's an incoherent position for cases where the contract was based on a shared false belief.
Two people both believe that there are 1,500 pounds of cherries in a truck. They agree to exchange the 1,500 pounds of cherries in the truck for $5,000. It turns out, through equal fault, that they were mistaken and there are only 1,200 pounds of cherries in the truck. How can the contract be executed entirely as it is? Does the seller have to put 300 pounds more cherries in the truck? Or does the buyer have to take 1,200 pounds of cherries even though he agreed to take 1,500? Or what?
If a contract is based on a shared false belief, without which neither party would have entered into the contract, it's not possible to execute the contract as it is.