True, but they also validated it against generic facebook images; and compared the accuracy of humans on the (dating website) images to the established benchmark of human capability (which came out comparable). If there was something telling sexuality-wise from the dating pictures, then you would probably expect humans to be able to pick up on it as well.

(see author notes on this: https://docs.google.com/document/d/11oGZ1Ke3wK9E3BtOFfGfUQuu...)