LGBTQ+ (and variations) are more category than label. We combine our powers because we're all too tiny to deal with all the labels and violence foisted upon us alone. Whether you can choose one of the labels is a matter of debate within the category. For most of us, it's like breathing air for the first time: "oh, I'm not alone in this. Other people feel this way, and they've fought all these battles so I don't have to start from 0." To choose it without that experience is kind of weird, but I don't personally have a problem with it in most cases.
