I don't think anybody holds the beliefs that you are condemning. Everybody agrees that since Nikki was born with the body of a woman, Nikki should compete against women. When people say "wHy IsNt sHe CoMpeTiNg aGaInSt mEn?" they are attempting to expose the hypocrisy of the other side, because the fact that she competes with women and nobody contests it, demonstrates the fact that the Compete-By-Identification side still recognizes that nikki should compete with women because to do otherwise would give her an enormous and insurmountable disadvantage. Those who support competing by identification often refuse to acknowledge the advantage held by men, but in this case it is impossible to deny because competing against men would be a career ending move.
It is nothing more than an attempt at exposing hypocrisy, and the only reason its not completely ironclad, is because Nikki doesn't identify as a man, she looks the part, and she did stop identifying as a woman, however she gets off on a technicality because she identifies as non-binary. Part of me actually wonders if she would rather identify as a man, but is avoiding making an even more obvious hypocrisy, because it would be seriously ludicrous to identify as a man and choose to compete with women while advocating for transwomen to compete aginst women.
Everybody, including Nikki herself, knows that in the case she does want to identify as a MAN, her only options are to
1.) Commit to the blatant hypocrisy of competing as a woman and force trans advocates to basically lose every argument for the rest of their lives because this creates a completely inexplicable contradiction to their thesis,
2.) Support transgender ideology and compete with the men, just as she identifies, unfortunately this would cost her professional career, but it would be admirable to continue an amateur career in men's running and maintain ideological consistency.
3.) Tell nobody that she identifies as a man, continue competing with women. There is nothing wrong with this option by the way. It may be intellectually dishonest to not expose a truth that destroys an ideology, however its perfectly reasonable to have the mental health and safety of trans people in mind, and to let the illogicy of transgender-athletics to prevail for the sake of not hurting other aspects of transgender ideology.