In the mining industry nothing should be based on extrapolation....

In the mining industry nothing should be based on extrapolation. If we were dealing with gold you're effectively saying if I strike 4g/t over 20m it's perfectly OK to say that the same grade will extend over 1km. Why not just go all the way through to the other side! You are allowed to say "open at depth" or "open in x direction" to indicate you suspect it continues but you are not allowed to extrapolate. The very fact that you are effectively admitting they are extrapolating would give me cause to wary. Not to mention the comply itself specifically points out that while they have extrapolated they probably shouldn't because they know there exists higher flowing course sections.