The BK/bailout GM did stopped production of the class 4-7 trucks they offered. It was one way to cut costs etc. IHC toyed with buying the lines, but never did. The Contract with Izusu to build and market the LOC class 3-7 rigs also was severed. But recently re-signed if you will. So there may be a few class 4-7 rigs in the GM sales figures. Reality, probably very few.
SO yes, the GM sales figures will be low. Personally, If the list is one I have seen from "Light and Medium duty truck" which I have a freeby subscription too. The numbers are probably right. These figures are ment to show ONLY rigs in the 10,001 gvw to 32K gvwr ONLY!
Marty