The rationale for this is unclear to me. Can we review what the rationale for this restriction was? Does anyone recall?

We have a format where the literal nil value for the complex type wants to be "%WSP*;-%WSP*;" that is, a hyphen, but with surrounding whitespace absorbed.

We can model this a different way, but the natural thing to do is to model it as suggested.

(This also just happens to run on Daffodil - because we're not detecting this ad-hoc restriction - a bug)