The classification you stated was for feeder cattle. They don't have a classification for "Inferior" on the meat grading floor because of low marbling. The low would be "Standard", I think.
The DM (Double Muscled) cattle were not significantly heavier than the NM (Normal Muscled)cattle at slaughter, but they produced heavier carcasses and higher dressing percentages (Table 1). The increased yield of carcass weight was in part due to the increased amount of muscling in the carcasses. This was evident in measures of both ribeye area and ribeye area per hundredweight of carcass (REACWT). Measures of fatness were significantly lower in the DM carcasses, including external and internal fat depots. As a result of increased muscling and decreased fatness, the DM carcasses had two full lower yield grades than the NM carcasses. As the meat packing industry moves to a value-based system for purchasing cattle, muscling will impact price. Several packers are already utilizing REACWT in their pricing formulas, and thus carcasses from these animals may offer the advantages of more red meat yield and less waste fat.
The NM and DM carcasses were not different in maturity (Table 1). However, the NM carcasses had significantly higher marbling scores and quality grades than did DM carcasses. Quality grades for the NM cattle averaged low choice, while the DM carcasses averaged high standard. This again emphasizes the overall reduction in fat content of carcasses from DM cattle.