The DFDL spec states:

"In order to provide portability of a DFDL schema, a minimal or extended conforming processor must ensure that all the required properties, as defined in the property precedence sections, are present in a schema, even when those properties are not implemented. For example if the bi-directional text feature is not implemented, it is still a schema definition error if dfdl:textBiDi is not set to 'no' [on] an xs:string element."

Whereas Daffodil will currently fail if certain annotations are present at all, even if they would not trigger unimplemented behavior. For instance dfdl:lengthUnits must be supported, but dfdl:lengthUnits='bits' is optional.