If I were you, I'd write them - anonymously if need be - a letter saying you noticed this question on their application, and that you found it discriminatory and illegal. To illustrate the problems with it, inquire if they would ask the same question but in a way where "gender identity" is replaced by other characteristics. For example, would they ask prospective applicants

How do you describe the way you express your race in terms of behavior, appearance, speech, and movement?

How do you describe the way you express your ethnicity in terms of behavior, appearance, speech, and movement?

How do you describe the way you express your religion in terms of behavior, appearance, speech, and movement?

How do you describe the way you express your age in terms of behavior, appearance, speech, and movement?

How do you describe the way you express your sexual orientation in terms of behavior, appearance, speech, and movement?

How do you describe the way you express your sexual inclinations in terms of behavior, appearance, speech, and movement?

How do you describe the way you express your economic and social class in terms of behavior, appearance, speech, and movement?

How do you describe the way you express your current income and level of wealth, or lack of wealth, in terms of behavior, appearance, speech, and movement?

How do you describe the way you express your political views in terms of behavior, appearance, speech, and movement?

How do you describe the way you express you health status - including, if applicable, your physical disabilities, mental health issues, current medical conditions, past medical history and/or your status as a carrier of certain disease-linked genetic anomalies - in terms of your behavior, appearance, speech, and movement?

How do you describe the way you express your plans and potential for having or bearing children in terms of behavior, appearance, speech, and movement?

If you write such a letter, my unsolicited advice is don't just send it to the admissions office. Send it to the entire administration, the school's legal counsel and its insurers, as well as to the school's and the local media and to publications/orgs that are involved in monitoring what goes on in US higher education. Also, send a copy to the Heterodox Academy and Jonathan Haidt. And a lot of other people bringing attention to disturbing trends in US higher education.