If I was to guess it would simply be that the 'tweaking is ongoing". What is missing, or what the tight lipped part is - tweaking for whom? Tweaking in what manner/ Effect on pricing for this tweaking? Is an off-take or buyout contingent on the tweaking? All valid questions but ones that cannot really be publicly answered. The only thing we know for sure is the insiders know a hell of a lot more than we do.
The PEA is obviously a significant milestone and we can only hope that Sandra's somewhat off hand comment "that the tweaking is bing done to support higher prices than the $8500' is the real reason behind the delay. Every $1,000 increase in average price increases the insitu value by $1.5 Billion. Thinking of it in this manner makes one really notice the imporatnce of maximizing the sales number. That is the equivalent of 1.15 million ounces of gold (for each $1,000 of price). Again, very very significant numbers, the most important number. The cost can be $1000 per tonne or $1500, it won't matter much. But add $2,500 to the $8,500 and that is monumental.