It's possible that it was created, then, in the wake of the December 1997 flap over photosensitive epileptic seizures being induced by "flickering" effects in anime (both Pokemon and, to a lesser extent, YAT Anshin were implicated). Pokemon was pulled off the air for four months, and other studios were instructed to avoid using the effect in future. (And The Simpsons had a field day with the controversy.)
I've seen negative-color images of The Light Card from Cardcaptor Sakura that I assume were made to be used in a magic duel, alternating with true color cels, to show the entity "powering up." But in the end only the true color ones were used.
As WeiBkreutz ran in 1998 and so was probably in production when the Pokemon panic erupted, it would make sense that other "flicker" effects might have been planned for this series, then discarded.
