It can't, because other conductive elements turn into SPRK, a completely different element, with a ctype of the original element.  A WWLD signal, on the other hand, is still the same element, just with a ctype.  The Clear SPRK function can only clear SPRK; a WWLD signal is not a SPRK, therefore the Clear SPRK function can't clear it.

Ok, what i mean is, it could be expanded to also clear ctype of wwld