The usual process is to base the overall pit on a "shell" (final...

The usual process is to base the overall pit on a "shell" (final pit outline) that will make the returns required at your predicted gold price (the optimum pit). Normally, you would then run a series of "nested" shells that use a series of lower gold price to show what sections of the pit could be mined at lower prices or make more money at the predicted prices. These "Nested Shells" would guide any cutback strategy that could be used to increase NPV by bringing lower cost ounces forward. They can also be used to assist and guide the schedule that should aim to even out the strip ratio (stripping costs). It is very unusual to start a pit at its final design limit at the surface because, as pointed out, it involves a lot of cash up front when mining at what would normally be a strip ratio well above average. I admit, I was surprised when I saw photos of the pit that appeared to show just this (but I may have been mistaken). On the opposite side of the coin, if they did take this approach, the costs going forward will reduce substantially.
As for the underground, I have said before that the Golden Age is more complex that people appreciate. I also have high confidence in the remaining reserve at Wiluna and in the treatment process's capacity to recover the refractory gold. The plant worked well right up to closure except when the then MD wanted the tanks emptied on a regular basis to find the "lost gold" (which wasn't lost at all).
All just my opinions but based on a fairly detailed knowledge of the industry and the operation.