Thoughtworks wrote in an email to me that they were only considering non-male candidates because of their quotas. The idea, I suppose, is that I should be willing to change my gender if I'm really interested in joining.
If they had quotas, they were made up internally. But more likely they were just lying to you, or the person who sent the email was twisting the truth. I don't think anyone but you thought of the "maybe you should change gender" bit. They just didn't want to hire you, personally.
I spoke to a bunch of lawyers who all told me they hoped I found some lawyer who would do that. The EEOC decided that if a manager directs their reports (engineers) to advertise a position, then people apply to the position as directed by emailing the engineers, then the engineers say some stuff about gender quotas, that's fine, because the applicant didn't fill out some other form and the company disavows this recruitment process to the EEOC while using it to source candidates.