You might want to consider what effect the endless insistence work in tech requires some sort of religious levels of 'passion' has on women or beginners or really anyone from an atypical (for tech) background looking to enter the field.

Yes, in the absence of strong evidence I would assume both Etsy and every other salaried company that permits offers to be negotiated is paying men and women non-equally for equal work, primarily because (as Greenspan points out) the market value of men is higher: they are receiving competing offers from places that are more blatant about paying men more (or extending fewer offers to women, or whatever). Hopefully this difference is pretty small at Etsy, but it almost certainly exists, and even a small arbitrage opportunity is economically rational to capitalize on.

I'm using "equal work" in an informal sense. (In the legal sense, yes, equal pay for equal work is the law, but also in the legal sense, you can't give an immigrant worker a green-card-path visa unless you can't find anyone in the States to do the same job, and we all know how creatively "the same job" gets defined.)

They could be paid equally, but the women will be better engineers. Because a man of the same skill level will command a more senior job.

They might also be implying that they are paid equally but on average do equal or higher quality work. Which isn't necessarily a bad thing because companies don't typically micro-manage salaries (for a given job title) according to individual performance.