Dropping 2/3 of the mass out of the driveshaft does amazing things for a RWD car, I know this from first hand experience. There's no reason why it wouldn't do the same for an SVX, particularly a 5-spd swapped one that had the stronger rear drive bias. The MK3 shafts available only use 1 U-joint per side, so one at the output shaft from the trans and one at the differential. Many people hollow out the old carrier bearing to act as a driveshaft loop.

From what I read, GM used those shafts for parts simplicity, (elimination of the carrier, etc) drivetrain efficency, and NVH all in one fell swoop. Because of the sheer volume needed they got production costs down to where it was feasable and with the elimination of the carrier bearing and what not it was actually less expensive when all was said and done!
I found it hard to believe myself, but Tom called it.

There's many other examples of similar driveshafts now currently in cars such as the 350Z.

I'd love to see some before and after results from one of these, I know any 5-spd swapped SVX would love the difference.