You probably do not see cut off grade references for chromium but it is a common practice in the precious metals arena. It is stated when calculating economical resources as in 43-101 compliance.

A company can say that they have 0.2 grams of gold per ton or up to 0.5 grams of presious metals per ton but with current metal prices these grades are not viable hence including them in a resource calculation is deceptive and non compliant unless one sugar coats it in some manner.
So when one calculates, the cut off grade is stated to inform the reader as to what grades were used for the calculations.