Why doesn't NOD32 have gen signatures?

Why doesn't NOD32 have generic signatures for RBot, SDBot, etc. like Kaspersky and McAfee do? RBot and SDBot are common pests, and NOD32 is having to rely on heuristics and pumping out signatures for every new variant while Kaspersky and McAfee are able to pick out these new variants with their generic detections.

 

In this specific case what would be the advantage between a generic detection and a heuristics detection of these types of malware? Would the generic detection be better?

Examples: http://virusscan.jotti.org/

Last piece of malware found was Win32:SpyBot-A1045 in rBot2pedper.exe, detected by:

Scanner Malware name Time taken
AntiVir X 0.48 seconds
Avast Win32:SpyBot-A1045 1.53 seconds
AVG Antivirus X 0.53 seconds
BitDefender Backdoor.RBot.D7C2C6C6 0.57 seconds
ClamAV X 0.62 seconds
Dr.Web X 0.87 seconds
F-Prot Antivirus X 6.67 seconds
Fortinet X 0.44 seconds
Kaspersky Anti-Virus Backdoor.Win32.Rbot.gen 1.07 seconds
mks_vir X 0.27 seconds
NOD32 probably unknown NewHeur_PE 2.12 seconds
Norman Virus Control Sandbox: W32/Spybot.gen3 15.48 seconds


Last piece of malware found was Backdoor.RBot.BE7215B2 in neukenmaar.exe, detected by:

Scanner Malware name Time taken
AntiVir X 0.40 seconds
Avast X 1.53 seconds
AVG Antivirus X 0.45 seconds
BitDefender Backdoor.RBot.BE7215B2 0.52 seconds
ClamAV Exploit.DCOM.Gen 0.64 seconds
Dr.Web Win32.HLLW.MyBot 0.85 seconds
F-Prot Antivirus X 1.18 seconds
Fortinet X 0.45 seconds
Kaspersky Anti-Virus Backdoor.Win32.Rbot.gen 1.15 seconds
mks_vir X 0.42 seconds
NOD32 probably unknown NewHeur_PE 0.68 seconds
Norman Virus Control Sandbox: W32/Malware 17.