I'm sorry, if a person you can tell easily at first glance to be a woman can at the same time 'effortlessly pass for a man' then all it does is highlight how absurd most of these claims of what's "feminine" or "masculine" when it comes to looks are, if there's so much of apparent overleap between these supposedly different traits.
Honestly I had to really look to SEE that she was female, and all her feminine features could easily be on a softer man. If all these people look at her and don't immediately see a woman, have you considered that perhaps you are either more discerning than most people are, and thus are wrong in your statement it's immediately noticeable, or that maybe the feminine traits you see are not as feminine as you think and are shared traits with many women and some men.
Just because you can easily tell she's as woman at first glance doesn't mean others can, and if enough people can't, making the claim it's completely clear is clearly false.
Androgeny is not a bad word, there are lots of traits shared between men and women, and a man or woman can have a lot of these traits, the more they do the easier they can pass for the opposite gender. There are masculine traits which = Is found more common in men. There are feminine traits which = is found more common in women, and androgynous traits, which is found relatively equal in, is shared by, or can fall into both masculine and feminine ranges.
People fall all over this spectrum. This is because physical/mental sex is not really so binary, it's a lot to do with hormones during multiple stages of development as well as many other factors. Take myself for example. I'm a girl, I have XY genes, but mentally/emotionally I'm female, I can't give the exact physiological reasons this happened, but I cannot be happy living as or identifying as a man, the male body feels wrong on me, I feel sick when I'm forced to live as a man. I have features naturally that are both masculine, feminine and androgynous, everyone does in different amounts.
Am I offended by my having masculine traits? No I recognize them, and being who I am work to get around them. Am I less of a woman because I have them no. So realize I'm not calling her less of a woman when I say she's very androgynous. I'm saying she has more traits shared by both genders, and as such passes easily for a man effortlessly. A man similarly androgynous can do the same just as well. Is why she's a bad example, she could be an androgynous man just as easily as a woman in that picture. Her gender is not so easily identified at a casual glance for most people in that outfit with her features.
Once again this is not a judgment on her as a woman, it's a recognition that men and women can look very similar sometimes and in her case is one of those times. Male and Female does not have a clear gender binary, there are points in the middle of both where they combine and a lot is shared. Male and female is not that simple. Trust me I wish it was, and I wouldn't have to struggle with my real life issues in this matter.
You're talking to a person for whom, passing as a woman is a very real and important concern, so I'm pretty aware of what is distinctly feminine and what is not. It is my life.
So you may immediately identify her as a woman in that picture, but it does not make anyone who does not, or sees her in a more androgynous light, wrong or trying to insult her. They just don't see it, because gender identity is not really that clear in a lot of cases to a lot of people. Stop trying to turn people into sexist monsters when they are just confused by that border between genders being no where near as clear as we try to pretend it is.
If a picture to represent women in armor commonly results in an awkward and sincerely confused: "Um... are you sure that's a woman?" is clearly an issue, and makes the picture a very, very bad example.