So I took the quote to mean "among the gifted, an early reader isn't necessarily more gifted than a gifted child that doesn't read early". Among that population, you can't pick the early readers from not by 4th grade.
I think it would have been less bad if she'd been saying that, but the quote about early reading as a milestone makes me think that she was talking about all kids.
Either way, your note about people believing that the statement applies universally is spot-on.
How come no one ever says this stuff about gifted athletes?
Val