The Seattle Times adds a detail that isn't in other articles: the off duty pilot had successfully shut off fuel flow using the same handles:

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To activate they must reach up and pull the handle down and turn it to lock it in place. Pulling the handle cuts electrical and hydraulic power to the engine and closes the fuel line.

Turning the handle then releases a pressurized bottle of fire-suppressing halon gas.

Alaska Air spokesperson Alexa Rudin said via email that “fortunately some residual fuel remains in the line, and the quick reaction of our crew to reset the handles restored fuel flow and prevented fuel starvation.”

https://www.seattletimes.com/business/boeing-aerospace/alask...