Headline is a bit misleading. They aren't really asking if you're trans, they're giving you the option of choosing it as your gender. I really think they were trying to accommodate trans people - so they're not forced to choose a gender they're uncomfortable with.
Of course, they probably didn't ask any ACTUAL trans people when they did this so of course they botched it royally.
The moral of the story: If you want to know how to accommodate trans people, ask us!