The sites that say athletes should still be within the specified BMI range are ultimately denying the fact BMI does not differentiate between fat and muscle, never mind that it doesn't take into account "bone structure" and other quirks. Blood pressure, heart rate, body fat percentage, and one's waist:hip ratio are more reliable indicators for health as they are not as easily confounded by muscle, and even they are incomplete.
As for what is attractive, people aren't looking around and thinking, "oh, she's hot, she must have a BMI of 19." People have their own standards for physical appearance and well-being, and I don't think many people have their own line up closely with BMI.