Need to update ARIA Best Practices for Tree mantioning aria-level?

http://www.w3.org/TR/wai-aria-practices/#TreeView

points to http://codetalks.org/source/widgets/tree/tree.html

which uses grouping containers to do nested leveling (and leave to AT to determine nesting level by sniffing it from DOM Hierarchy) like http://www.w3.org/WAI/PF/aria/ spec says.

Unfortunately,  http://www.w3.org/TR/wai-aria-practices/#TreeView seems not to recommend using aria-level on the nodes (whereas it has been added in other ARIA trees, see DOJO example http://extjs.com/deploy/dev/examples/tree/aria-tree.html ).

So, should the spec been updated mentioning that aria-level should be also used? Or is this superfluous?

Comments?

- Stefan