I just gave the final vote to close on this question through the iOS app. As it doesn't show the number of close votes already, I was curious to see the status so I opened the question in Safari.
There I saw I was the final voter on that question, so the question got closed. The UI in the app wasn't updated though, like it does in the web site. When I refreshed the question manually, it did show the 'closed banner'.
I don't know whether this is considered a feature request or a bug, but either way: can this be added please?