I think the argument is that the end users wouldn't be able to manipulate the table in ways other than flipping bits, and that the system should be able to support any combination of bits.

In reality (and I think this is your point) the consequence is that just because a system can support a particular combination doesn't mean it makes any sense for the problem domain. Therefore by exposing this to users without tests, they can screw themselves over, even if the system continues to "work."