Many samples from XVirus' database (that's just a text file with MD5) are available at
http://virusshare.com/
It seems he removes old checksums, I see only the newest hashes from VirusShare in viruslist.db. I assume he's going to VirusShare from time to time and grabbing latest files.
I think that the samples that were tested are in VirusShare (or another know malware database), that's why all were detected.
I scanned some fresh samples using it (I submit samples to VS, but these weren't processed yet) - nothing was detected.
Malwarebytes doesn't target files older than 3 months. So if some files were old, then that explains the result.