I didn't know if this was played right so that's why I waited a week to publish it. It turns out that it was played right - for the Imperial side to win, a Rebel hero only needs to be "defeated" once (in other words, flipped to the wounded side, not "defeated" a second time and "withdrawn).

See page 8 of the "Learn to Play" guide under "Defeated":

"When a figure has suffered damaged equal to its Health, it is defeated. When a hero is defeated, he becomes wounded..."

On the same page, under "Wounded", the last sentence says:

"If a wounded figure is defeated, he withdraws."

Anyhoo, here's the video:

https://www.youtube.com/watch?v=exoi4mGWj14&feature=youtu.be