All tabs for a resource (Overview, FAQ, Updates, Reviews, History) show the "Unmaintained" label except for the Discussion tab. It is pretty important it displays on the discussion tab since by the numbers it is typically where you end up when using search.
Makes sense why it currently isn't showing. I would think with a couple lines of code the forum software should be able to check the resource status within RM and display it as unmaintained on the Discussion tab just like the other tabs.