Because all you ever hear about Jobs is that he was a dominating bully. She shows that people did stand up to him (at least when the facts were on their side).

That's not surprising if you've read much about Jobs, especially the Isaacson biography. Jobs generally respected people who were confident enough to stand up to him, and he surrounded himself with good people who could do just that.

Joanna looked like she was about to lose it when he interrupted her, but she let him continue. Even she seemed to know when arguing with Jobs was pointless.