Interesting they've gone to the effort of recreating the redundant plinth. I know it used to have a smaller version of the main desk on it - but was it ever used for anything?
It was originally used for Counting the Cost. The desk was skewed at an angle with white lighting. I thought it looked really nice.
I remember an insider posting on here (or perhaps it was on another site) years ago that they originally planned to also use that desk for Inside Story with it spun all the way around for a newsroom backdrop. I don't think they ever did, and they actually used a very convincing key for the newsroom/control room backdrop in the first few years of the show.
There also was a presentation area in the mezzanine. It was used briefly for headlines early on, as well as Sportsworld, which was eventually canceled after a few years.