The optional ORDER element is omitted at formatting time. This element does not add any information (it is totally redundant with the AXIS position), is a distraction for the human reader, and its support would require new API in the Formatter class. Until now we were able to work with tree structures and ordered sequences only.
Support of ORDER element would force the introduction of the concept of List (collection with index) or array structures. We are a little bit reluctant to impose this restriction in the API only for that element.
Update (May 2015): now supported.