It doesn't make any sense to me that you'd need to use the choke to engage the blades without killing the engine. Sounds like either a carburetor issue or maybe even a governor issue.
I think the shop is trying to pull a fast one by telling you to just use the choke. That's BS. And this is an instance where it's so good to be able to tell them with a straight face that you have not played with any of the settings whatsoever. They can't turn it around on you and claim you're the one that messed it up.
That's what I was thinking too. And I don't plan to play with any settings, for fear I may break something and/or void the warranty. I'm just not sure what to do about it now.