Linux NAS 126.96.36.199-arm1 #32 Wed Jun 24 15:19:48 CST 2009 armv5tejl unknown
That seems like a very old kernel.
We're at 2.6.36 with an average of 3 months per release. So that's 24 releases back -> 6 years? (indeed almost right, 2.6.12 was released june 2005).
I don't actually know, but I would be entirely unsurprised to learn that a kernel that old doesn't support (or incorrectly supports) tunneling raw scsi commands (ie. smart commands) to the destination device (ie doing raw scsi over usb).
Please note that I'm totally guessing here...
Would upgrading the NAS to a newer kernel version be _very_ hard??? [guessing so...]
What type of NAS device is this? Does the manufacturer have a newer firmware image available?
[of course the problem could also be that it's arm, and not x86_64, but...]