It is obviously not the case that women are equal in our society. Additionally, then, my town shouldn't have a big placard that says "home of Olympic gold medalist [some person]" since obviously being from my town is equal to being from the one over. But we do typically care about these sorts of things, and we care about the oldest person to be president, the youngest, the first gay, Catholic, whatever, black president. We care about coincidences, streaks, and firsts of all manner and no one has to point out that that it doesn't matter "X will be the first foreign-born CEO" or whatever it is. To assert that being a woman specifically is not notable feels like it just serves to downplay people's accomplishments when those accomplishments are made by women.
The fact that people are discussing it, and so agitated by the use of the word "woman" shows, if anything, that they aren't equal and there is still much work to be done.
Articles like this enforce that inequality. I'm 100% for equal rights, equal opportunity and equal recognition, unlike you, or the people that write articles like this. The use of the word "woman" implicitly means "this has been done by men before". And in that case people like you find it remarkable simply because it was done by a woman, which is enforcing inequality. If you want equality, change the title to "US woman becomes first person to walk in space and dive to deepest part of the ocean". That's (arguably) notable and doesn't imply that I'm congratulating her because she did it despite being a woman.
Until and unless society truly has equal rights/opportunity/recognition, it behooves us to fete those who do the very hard things, with an extra helping of overcoming institutional/societal barriers due to their inherent characteristics.
It gives hope to those who fear that those barriers are so large as to be insurmountable and without which many of those would choose not to try.
Saying we don't have equal rights is a serious claim and one that would need backing up.
As for equal opportunity and recognition, I would say it's often skewed in favour of women right now. A woman can find a job in tech quite easily because, for some reason, companies want to hire women. That's not equality. Recognition is also higher for women. Women don't have to be first or best to get recognised, they just have to be the first or best woman. There's no such thing as "first man". It's often repeated that the first programmer was a woman. OK, so who was the first male programmer? Nobody knows or cares.
