Potential Upside of WKT - Expandable Graphite, page-2335

You've obviously misunderstood or missed some of wkt's older announcements about their choice to use a 10% cut-off grade. They have said all along that they will stockpile lesser grades and may use them later on.
From a theoretical perspective you should mine to a cut-off point where the marginal revenue is breakeven - however with limited plant capacity the optimal choice is to use a higher cut-off since our high grade core is so accessible.
Noone has ever implied it is not economical for Wkt to mine grades at say for example, 8% tgc.
This is just you taking a theoretical principle and applying it out of context to downramp Wkt.

Like shooting fish in a barrel.

GLTAH