Hi,
I think it is good to have the course based on the system one is going to use. Seen people from AIX world completely wasting their time on TSM/Windows course as they were battling with the OS instead of understanding the TSM (can imagine vice versa situation).
But does the OS selection really matter?
If you look at the differences - device drivers, path definitions, starting/stopping the service(s) - that is all! Once TSM is installed and running, you can learn it without knowing the underlying OS. Stgpools, policies, way how it works ....
Differences can be covered at the end of the course.
There is one reason against Windows - wizards. Too many people rely on them without understanding what they really do.
So my selection is Linux.
Harry