Yeah its true,but not totaly...
Win2003 Server had some small error and Virusbulletin staff didn't ask Alwil team how to use Avast! correctly (something like this,ask one member of Alwil or search for that Topic),for NT i don't know exactly.
Most important is that it passed on Windows XP platform which is widely used. Who use Windows NT anyway if you can have much better Windows 2000.
Check the Norton and you'll see that it has better PASS/FAIL ratio,but we all know the Norton is the most terrible antivirus,so don't take these results as 100% reliable.