I have to say, I question the results of this survey, too. I know that when it comes to providing personal care to patients, most males rarely request their caregivers be only male, and many prefer females. For women, I've known of many who are not comfortable with male caregivers. This is different than doctors, of course, but much of the nature of the care is similar.
I heard some discussion of this survey in the news, and it was suggested that women have become conditioned to having mostly male doctors because it was that way for so long, generations without female doctors being common.