I admit to giving in to a little sensationalist temptation here.
Most drive manufacturers release diagnostic tools that can be run from a live CD or floppy. Usually DOS-based. In WD's case, it appears they do have those kinds of tools available, except for a certain line of drives. What got me was the quote:
We manufacture our hard drives, build our software and test them on Windows operating systems only.
Hopefully, this is just an "easy out" used by a support person to get rid of a pesky Linux user.