Our RI cleverly uses the same scanner for StAX and SAX parsing. Unfortunately, when the EntityManager calls resolveEntityAsPerStax:

        if (external) {
            Entity.ExternalEntity externalEntity = (Entity.ExternalEntity)entity;
            staxInputSource = resolveEntityAsPerStax(externalEntity.entityLocation);
            /** xxx: Waiting from the EG
             * //simply return if there was entity resolver registered and application
             * //returns either XMLStreamReader or XMLEventReader.
             * if(staxInputSource.hasXMLStreamOrXMLEventReader()) return ;
             */
            xmlInputSource = staxInputSource.getXMLInputSource() ;
        }

in the case where the resolver is in fact a SAX EntityResolver2 interface, it has no way of determining the entity name (because all that was passed in was the location). That means it can't construct the correct call to resolveEntity for SAX.