I honestly don't see how Jax counters Olaf. Olaf's Q and E are not blocked by Jax's counter. Jax TYPICALLY builds with ad/ap and uses his GA and ult for resists. Olaf's E is true damage so Jax's ult's active obviously does almost nothing. I am not saying that one stomps the other one, but they both can hurt each other. Jax jumps to Olaf and uses Counter, Olaf stands his ground and hits eith Q/E combo, both damage each other pretty well, both scale late game extremely well.