Ann: Borba Operations Update and Prospective Resource, page-156

Yes, I agree with you. And I had in fact anticipated this possibility wrt to the outcome pre-announcement.

On a number of occasions through my own career I've observed first hand how some consultants, not all, have erred on the side of conservatism with their conclusions. Obviously their professional reputation is on the line with every assignment, so to be conservative is a safe decision.
I'm not saying outright that on this occasion this is definitely the issue, but it certainly is uppermost in my thoughts, particularly when I see the use of Monte Carlo simulations being applied, potentially to moderate the outcome - it's just a matter of changing the variables bit by bit to get an outcome that provides a reasonable margin of safety (ie as a safeguard to any potential challenge down the track).