I honestly think it's very unlikely... I find it very hard to imagine that a guy would see a headline that excites him and then see the author's name and be like: "Oh the topic sounds very interesting, I would love to click on it, but it's written by a woman, so I will pass!"
As a woman, I think sometimes people take this whole issue of gender equality a bit too far. They probably mean well, I get it. But I follow a lot of female run publications, and I see plenty of female writers on my feed - and read them. If you don't follow any women writers, then I don't think you can expect to see a lot of them, it kind of makes sense.
You covered a lot of reasons that could affect the outcomes you saw. We can't really derive any meaningful conclusion unless we know how many writers on Medium are female vs male. Besides, I think a lot of men may simply not be interested in the stuff that women write about it - it can be that a lot of female authors write about relationships, emotions, mental health, and parenting, and men probably write more about self-improvement, business, finance, tech and productivity. So a man who likes to read about startups and innovation won't likely click on a headline about breaking up with a narcissist (or even see it on his feed). And you can't say he's sexist because of that.
Now, I am not saying that women write only about relationships and such - I am sure there are lots of them who also write on tech, business, marketing etc. But if I had to guess, I would hypothesize that it's possible the proportion is smaller. Some might bash me for promoting gender bias, but the truth is, I don't think there is anything wrong if it happens to be true - I am a woman, I work in investment management (a heavily male-dominated field) and my writing has nothing to do with my professional occupation: I write about education, toxic parenting, mental health, and self-discovery.