Since [most] hackers like to use the powerful tools that are Linux-only, silent rootkits rather than debilitating virii are the weapon of choice for infecting Linux boxes.
The researchers most likely used Linux due to being able to have access to the entire system source code, which I doubt M$ would have released for their research even if they were sleeping with Balmer.... However, you are correct in this potentially being an OS agnostic strategy.
Of course, for myself, why load up a system with anti-spyware, anti-malware/virus, root-kit disablers, etc, etc, etc and lose 30+% of system performance? Apparently this kit whacks 6% off to boot and we all know the opinion on the [lack of] performance of Symantec or the like.
Paris - yeah, you'd probably get a virus from her too.