You can assemble them both ways, but they don't "fit" both ways. I've seen
some aftermarket rebuilt axles that had the inner joints assembled wrong,
and they usually will bind up. If yours seems to be working ok, then you
probably got it right.

> So, is this 'mission critical'? What is the reason for
> the orientation as per the manual, and why the hell
> do the rollers fit both ways?!?!