Problem with property path test case pp15

I think there is a problem with pp15

SELECT *
WHERE { ?X :p{0} "o" .
         ?Y :p{0} :o .
         :s :p{0} ?Z . }

The query is applied to an empty graph and it returns:

"o"
  :o
  :s


However, the current SPARQL 1.1 Query document specifies:

Definition: ZeroLengthPath
A zero length path matches all subjects and objects in the graph, and 
also any IRIs explictly given as endpoints of the path pattern.


But literal "o" is not an IRI and it is not in the graph, so the query 
should fail.


In addition, what is the rationale for matching "IRIs explicitly given 
as endpoints of the path pattern" ?


Olivier