I'd be really careful about this one. I'm hearing a lot of chatter in the flooring community that this is a typical cash grab for unknowing folk. They rely on your fear of not having 'the perfect floor'. I don't know, I would ask that they demonstrate (in person) what the issue is and why it requires additional work.
Perhaps get a second opinion too? Assume everyone is trying to rip you off until proven otherwise. It's harsh, but I go into all my business agreements with that mentality. I am a cynic by nature though