I think it's quite clear in context that Spider (from the Secrets of Power) is not the same as Spider (the totem) or an Invae. A strong case could probably be made (based on its Name, and that being important when the book was written) that it's an aspect of the totem spirit though -- one intentionally walled off or separated from its more benign aspect(s). So Spider as the hunter and killer versus Spider as the builder, so to speak.
HMHVV clearly has a metagenetic factor much like the expression of Awakening. I doubt it's a simple manner to alter its threads (again, to use Earthdawn terminology) to allow it affect another class of creature -much less one that is inherently magical itself. Or, heck, maybe that's what the Aztlan anti-dragon bioweapon is based on HMHVV (vampiric regeneration being incompatible with draconic regeneration, so neither works). Plenty of room to explore the origins of that.