I don't think she means that you shouldn't know anything at all about photography. You obviously have to know how to see to be any good at it. You know, light, timing, personality, connection with the subject matter, empathy, all that is important obviously.
What I think she's referring to are those that focus too much on the technical side of photography too much, understanding how all lenses work, how the minute details of one developer is different from another, etc. At least that's how I read her statement. The more you focus on those aspects of photography, the more you will be distracted from focusing on what's in front of you.
That's obviously my opinion, and I can't read her mind.