{{#subobject::}} vs {{#subobject::-}}

From semantic-mediawiki.org

The syntax for anonymous identifiers used to be either {{#subobject:-}} or {{#subobject:}}, i.e. either a hyphen or a blank. Apparently, the documentation no longer mentions the former. Why so? Will it be deprecated in SMW 1.9?

09:31, 7 September 2013