Bit late comment on a relevant topic.
The NHLA manual on grading made for me very interesting reading. It seems primarily to provide minimal criteria on hardwood grades, to address the situation where manufacturers of [kitchen] cabinets and floors purchase wood without first having inspected it.
While the NHLA criteria are rather relaxed on warp (½” to be lost for an 8″ wide board) and appear absent on grain direction, they still impart benefits – particularly within the EU. Grade FAS (both faces good, i.e. free from knots over several feet) can probably not be achieved without the wood being more or less straight grained; and as the EU have no guidelines whatsoever, but demands many popular hard woods imported from North America to comply with NHLA, I can North American wood that is superior to their European counterparts, at a lower price. (Been waiting eight months now for the European Commission to justify the EU position).
London, UK; Boston, MA