We make an O-face only at orgasm for an obvious reason: it is too ugly a face to make during sex. A true, uninhibited O-face is usally rather ugly. If we made it during sex we'd turn off our partner and the sex would stop.
The O-face is the biological moment when you are not in control. You are a vessel for orgasm - plain and simple. A slave to reflex and release. It's pure and surrendering, like a sneeze. If you snap shot the O-face out of context it's rather icky. The eyes lock in place and go dead. The mouth twists; the brow clenches. Some drool, some shake, some snort and squeeze their features together as if they'd just been asked to "make the ugliest face you can."
Yes, nature is a clever one. If the O-face was sexier we'd be turned on and have to have sex again. Like, right then and there. Who could do that?
Lol at the article, but I happen to like my bf's O-face. I don't how or why, I just do.