"Just keep in mind that at (the real) HM- the targeted copper is thousands of feet deep- maybe as much as 5K."

That is partially correct because it is historical information about the Porphyry deposit.  Since then, I believe JB and our then-outside consultants offered from remote sensing that the site may include a copper skarn deposit on top of a portion of the deeper material.  This is similar to some other porphyries around Arizona and the world but is not typical.  Such can add significantly to value and lower the overall cost of mining. 

https://geologyscience.com/geology-branches/mining-geology/skarn-deposits/