The quarterly was legal, just misleading, misleading to quote cash cost and not total cost, misleading to quote wmt for production but dmt for prices. I don't take into account improvements that management promise but haven't delivered yet, since most of them don't get delivered at the end.
If you are interested, have a look at SLR quarterly, they are much more honest and detail their cash cost, cash operating cost and "all-in sustaining cost" in the same table. Useful as a reference. All mining companies should do quarterly this way: