The issue that I think is highlighted by the article is that it presupposes that the transathlete is undergoing hormone suppression. That isn't a prerequisite to participate in most sports, and to require it would require disclosing more detailed medical information than might be prudent.

So, while the study is small, it is also not representative of many instances of trans athleticism. A transwoman not on HRT is just as much a woman as one who's been on it for years, according to advocates, and should be equally eligible to participate in women's sports. If that belief isn't held, you'll be labeled a transphobe and bigot as well. ¯\_(ツ)_/¯