In the course he states that the player with the K needs to call 50% of the time to avoid being expoitable. He arrives at the 50% because at this frequency the bluff with the Q is 0 EV.

But isn't there something missing? The range of they polarized guy can't be neglected, for example if it consists of 4 Aces and 1 Q.
Than the player with the K should always fold to a push even though calling 50% would give the bluff 0 EV.