It's sarcasm. "I interviewed all three women who attended" as in: there were hardly any there.
It's also irritating to read, as there were a lot more women devs this year at WWDC compared to the past three I attended, and Apple employs a lot of very talented female engineers that showed up for sessions and labs. Not sure what prompted this increase (the iPhone? :P ), but it was really nice to see.
My estimate of the percentage of women at WWDC is 5%.