I emailed Champion tech support quoting the shut down instructions from the manual. Here is the reply.
"Hello,
No it not a mistake. If you are using the generator throughout the day just use the on/off switch. If you’re putting it away for a day or longer we instruct to turn the fuel valve off and run until fuel starvation. This does a few things:
1) Allows generator head to cool
2) Allows engine to cool
3) Leaves carburetor bowl and fuel line dry.
With the introduction of ethanol you cannot just simply turn off the product and allow the fuel to sit, especially un-treated fuel. Areas with high ambient temperature and high humidity can start having fuel issues in about 3 weeks.
Please give us a call on our toll free support line at 877 338-0999 ext. 401 if you have additional questions or concerns.
Thank you for purchasing a Champion Power Equipment generator.
-JMM Champion Tech Rep"