I don't pass yet in pictures, and yet in person, I pass very consistently. Granted I don't pass as an attractive woman (haha), and I think it is mostly thanks to my voice and other cues that don't show up in pictures.
I have met people who, opposite to my case, actually don't pass in public because of factors that are not captured in pictures, and yet they look like supermodels behind the camera.
I think regardless, unless the person is soliciting critical feedback, it is important to be gentle about whether or not they're passing in a picture, and to make it about what they could do to feminize themselves further to be passable based on the picture they're showing. Saying simply the person doesn't look feminine, without necessarily pointing out things about them they can augment, or things that are already working for them, is shortchanging them and potentially hurting them too. Just my $.02.