Ann: Positive Drill Results at Northwest Anticline Target, page-16

That is some deep drilling....  but it's worth remembering, the scoping study never envisaged this being open cut:

"The minerals of value are contained in the Dolomitic Ore Formation (DOF), which is a moderate to steeply dipping mineralised zone that persists over an extensive strike distance and outcrops at surface.
The Study, including preliminary project capital expenditure estimates, mining and processing costs, has been completed to an accuracy of +/‐40%.
Potential open pit designs that were investigated contained a significant proportion of the oxide ore type, which demonstrated sub-optimal recoveries in the limited metallurgical test work done to date. Additional metallurgical test work is required to further investigate open pit opportunities, in conjunction with an updated mine plan incorporating the planned updated Mineral Resource. The Study therefore currently focuses primarily on underground mining as the base case."

Whether it's 100m, 500m, or 1000m down, underground is underground.

As to the value of drilling that deep right now - I guess they could have drilled four shallower holes and confirmed the resource closer to the surface, but my take is that were wanting proof this thing is a massive vein that runs for a great distance.  And the only way to do that, is to drill deep and intercept it.

DYOR-GLTAH