It's a combination of a few things IMO: depending on the ground...

It's a combination of a few things IMO: depending on the ground type, it dictates the angle of repose/embankment angle, which dictates how far you need to dig outwards. If we already know we will move surface soil, going further down is a lot more feasible than if the gold was not at surface level.

I am excited to see the extent of gold proliferation at depth. We may see a high grade fault but as @danbradster alluded to, it will need to be either massive, or very good grades to excite the market. Economically yes, it's better to have surface hits to initiate production. But knowing that there is gold at depth makes the nerd in me giddy.