I wouldn't trust the XRAY book. Lots and lots wrong in it.
Your observation is pretty much correct. A stood up shock will be effectively stiffer at the wheel, and stiffer settings give more "response" (initial turn-in), but less "grip" (mid-corner).
There is also a small effect on the progressiveness of the wheel rate the more the shock is angled, but since very few cars use extreme angles I doubt it would be something you would notice. It is relevant to something like the old Schumacher Cat 2000 which had almost horizontal shocks.