I think you might be struggling to get your head around in situ...

I think you might be struggling to get your head around in situ resource and lake bed area.

If Mackay had the same grade and yield as LD, AMN could boast that it could potentially produce three times the annual output as RWD.
Mackay has over three times the area but can only produce the same output because it has lower grade and yield.
The large lake/more trench argument is a myth. It's like stocking a 100 acre pond with a dozen fish and stocking a 30 acre pond with 15 fish and saying it is going to be easier to catch half a dozen fish in the bigger pond. The fisherman is going to spend more on bait and fuel for his boat in the bigger pond.