(Possibly NSFW) How is it possible that adults can be confused about what female genitalia look like?

http://www.huffingtonpost.com/2012/05/24/yearbook-photo-lake-norman-high-school-genitals_n_1543023.html?icid=maing-grid7%7Cmain5%7Cdl2%7Csec1_lnk3%26pLid%3D164463
There seems to be some debate about whether or not this female student was flashing her goodies at graduation. Assuming that about half of the people reacting to the picture are female, they would certainly know. If the other half were men, at least a high percentage of them would know too.
So what is the confusion here? It either is or it isn’t. Why is there this confused debate?