Yes, I've heard that said a hundred times. She should only mention that she's coming to live with her husband.
I also read (and I wish I could find it) that having a job lined up increases the chances of being approved. It's a typical governmental case of being dammed if you do and dammed if you don't.
I think, for an initial application, I wouldn't mention a prospective job. In our case, this will be an appeal. I believe it will be a mediation style appeal with me and one or more immigration appeal board members. In that case, I could go on to explain that this job is not the main reason, or even a guaranteed thing - it's just an opportunity, if she wants it, if she has spare time, and after she's become comfortable in her new home. I believe we will also be given the opportunity to have a translator phone my wife and interview her. In which case, she can reiterate what I just said.
I fully intend to explain to them that all we want is for my wife and her son to come home. They aren't looking for welfare money. They aren't trying to take away local jobs. They don't plan to hit the ground running, and disappear into the wood work. If they just give us a chance to explain that this is a real relationship; that after 7 trips to China, we're more than committed to each other, as husband and wife. I don't know what more we can do. Maybe I'll have to get her pregnant.