They are miners, so they look for the resource they're 'mining'...

They are miners, so they look for the resource they're 'mining' for. It's not an objective geological survey of the landmass.

The whole point of assaying rock chips is to confirm the presence of the resource, that's it. So then a decision about drilling is taken.

You're talking like we're assuming, because there's rock chips, there must be a motherlode. No one rational has said that. Drilling will tell that for sure. Until then, a decision has to be made, based on the chips assayed, is a drilling program warranted? Most in here would agree hell yes!