Yup, it's entirely unknown. So reading it as implying any sort of exception or special rule or extension or whatever is logically invalid. We just can't conclude anything from it.
I believe the only magical residue with a game effect is powerful rituals effect on aura growth.
That requires a major assumption on just what "magical residue" is.
E.g. What if the faerie has a power such that when it dies any of its remains that are eaten, used as fertilizer, etc. have some sort of magical effect on the consumer? So the residue is magical.
Also, it should be pointed out that Traces are referred to as "residue" of magic as well, and there are game effects with regard to Traces.
The dye for Tremere robes also used the term "residue" and comes from a magical source, though I'm not sure there is a true game effect for it rather than just flavor.