You're incorrect. This us from the runner's Instagram account:
nikkihiltz
Not he, not she, just me. When I was born I was named Dominique Ann Hiltz and assigned female. The thing about names and the gender someone assigns based on your sex is that sometimes they fit, and sometimes they don’t. Just like many people feel more like themselves going by a different name than the one they were assigned at birth, some people feel the same way about their gender. For me, it happens to be both! Just like I’ve never quite felt like a “Dominique”, I’ve also never quite felt like a girl. My birth certificate may say Dominique and female but I say, my name is Nikki and I am non-binary.
Then she is not transgender and the whole thing is a hoax.
And by the way, it looks like a dude. Must have been taking hormones all this time which should disqualify, whatever it is, from competition.