You may have a point. An IOU holder probably can't refuse a cash payment and then sue for nonpayment. But absent a debt, i.e. I offer to cut your grass for $20.00 but I want to be paid in kielbasa, all you can do is say yes we have no kielbasa and move on.
Reminds me of an old joke ...
Polish guy goes into a store and says, “I’d like ten pounds of kielbasa, please.”
The guy at the counter says, “You’re from Poland, aren’t you?”
The Polish guy says, “Yes. How’d you know? From the kielbasa?”
“No,” says the counter guy, “this is a drugstore.”