We can't turn back the clock, Glass.

The pit was dug at great time and expense, now let's get as many of nature's secrets out of it as we can.  

The various grades in other kimberlites are associated with different  geologic events, or different periods of lava flow. There was no indication that this sill has different flows, and this paricular location would be different than any other.  The other sills were most likely from a different time, so we would all expect the other sills to have a different diamond  content.

If we knew then what we know today they may have made different decisions.  But you make your decision with the best knowledge at the time, and adjust as you move forward.  We need to judge based on how they learn and recover from mistakes, more than from the mistake itself.

Ted