Stopping an opponent from challenging with the Boost ability can be a huge advantage, protecting your characters from a lethal threat on the board
Even as the insta-kill target of most pods, at a 4-drop this might be an inexpensive Beast to weed out any removal in prep for a bigger closeout
Its limited print run and unique presentation make it a valuable and sought-after addition to any collection.
Without data on all the huge callings ever made, we may never had a definitive data-driven answer
(If a permanent with a stun counter would become untapped, remove one from it instead.) If all targets of Crashing Wave become illegal before it resolves, the spell will not resolve at all and you will not distribute any stun counters, even if the opponent still controls some tapped creatures
Not as bad an outcome, but still not good