I say cash loosely speaking. You at least cannot pledge income from debt that is presently being negotiated down or cancelled. That kind of thing isn't "value" because it's imaginary.
Debt can absolutely be sold for whatever it is worth. In this case, the Jones' debt owned by the Sandy Hook families is fairly valuable to Jones' other debtors because it means they get a bigger slice of the bankruptcy estate. Thus the Sandy Hook families can offer enough of their Jones' debt in the sale to make it more valuable. (Edit: more complicated than how I explained it because both sets of debtors include Sandy Hook families)
This isn't any more "imaginary" than money itself.
Is this a legal term or something? Not to be rude, but who cares what you mean by it? It's totally besides the point
Obviously "loosely speaking" is not a legal term but I'm sure there is one that means the same. I mean you need real money to buy things, not bad paper. Bankruptcy does not exist to deliver good feels to people, it exists to settle financial matters as objectively as possible.