This is an interesting point. In almost every other aspect of life, we take pains to make sure that we are NOT defining what a person is. In all other aspects, we recognize that a person is a complex, multifaceted individual who is the sum of their attributes and experiences and character, and that no single label defines them as a monolithic identity.
But when it comes to gender, we're being asked to turn right back around, and make that single element of them as a person the entirety of their identity.
And then there's common sense. I'm an epileptic. It's not the only thing I am, but trying to insist that people call me a "person with epilepsy" is frankly dumb. Most of the time, my epilepsy is completely irrelevant. The only impact it has on day to day life is that my phone alarm goes off in the evening so I don't forget to take my anti-seziure meds. Oh, and I probably won't do a month-long camping trip in the outback or go sky-diving, and I don't much care for nightclubs with loud music and flashy lights that are likely triggers of a seizure.
But when it's relevant, it's perfectly acceptable and straight up common sense that I be referred to as "an epileptic".