The key part: "For most software, domain models are not real". Indeed, if your reality is ill-defined, you need miracles, aka invalid states, to handle certain practical cases. So it's more about admitting a design failure. One type of such failure may be putting wrong constraints on the model. You have to think hard about what can and cannot be, and often it's not a luxury your boss can afford. To allow representation of invalid states is to admit that you're going to be proven wrong eventually, which is not a wild exaggeration in a wide range of circumstances, alas. It's to plan for a mess, because a mess is inevitable.

(This whole approach reminds me of "I think therefore anything, due to the false antecedent".)