In NST's case, I am not sure what their milling capacity is...

In NST's case, I am not sure what their milling capacity is currently and I will imagine is pretty low. If this is so, it would not make sense lowering the cut off grade to rinse the extra bit of gold to increase revenue but also AISC. As @mainholm said, management would be looking at the mine optimisation process to adjust which is a skillful feature of management.

Regarding shorting NST, I see it like a typical shopper at Myer. If the price keeps rising then they think it is expensive and associate with over valued or in indicator speak over bought. In isolation this is a perfect sell or short. Ditto in a down trend. People loves discount, the greater the better because of bargain mentality. The oscillators would all be screaming over sold.

I'm no different sometimes and the figure 4 itself appears expensive in numerical terms compared to "1" so can be deemed expensive. Not a rational way to look at things.