The article is referencing this argument:

The International Olympic Committee (IOC) settled the issue of transgender athletes in 2004, when they released the rules for them to compete. The IOC rules boil down to three basic points:

They must have had gender reassignment surgery.

They must have legal recognition of their assigned gender.

They must have at least two years of hormone therapy.

Given these conditions, the IOC does not consider being transgender an unfair advantage. The IOC did, however, consider drinking too much coffee an unfair competitive advantage for nearly 20 years. The IOC still considers baking soda a potential doping agent, though. Many common cough syrups, lozenges, eye drops, cold medications, diet products, nasal sprays, and allergy medications will also result in a medical disqualification for being at an unfair advantage. Clearly, the IOC does not approach matters of unfair advantage with an under-abundance of caution.

The NCAA instituted somewhat less stringent guidelines in 2011. They do not require surgery, and they require only one year on testosterone suppression for male-to-female transgender athletes. The conclusions of the consulting medical experts on the NCAA policy were unambiguous:

"It is also important to know that any strength and endurance advantages a transgender woman arguably may have as a result of her prior testosterone levels dissipate after about one year of estrogen or testosterone-suppression therapy. According to medical experts on this issue, the assumption that a transgender woman competing on a women's team would have a competitive advantage outside the range of performance and competitive advantage or disadvantage that already exists among female athletes is not supported by evidence."

In an interview regarding transgender MMA fighter Fallon Fox, Dr. Marci Bowers explains why there is no effective competitive advantage in being a transgender woman:

"Most measures of physical strength minimize, muscle mass decreases, bone density decreases, and they become fairly comparable to women in their musculature. After as much time as has passed in her case, if tested, she would probably end up in the same muscle mass category as her biologically born female counterpart."

In the same interview, Dr. Sherman Leis concurred in all respects.

Indeed, given that women get 25 percent of their circulating testosterone from their ovaries, post-operative transgender women typically have less testosterone than their counterparts. Fox noted, "Any of the women I'm competing against, my testosterone levels are drastically lower than theirs; it's almost nothing."

Dr. Bowers agreed: "When you test her, she's going to come out with low testosterone levels and muscle mass that is remarkably similar to her counterparts." These observations were borne out in Fallon Fox's first defeat at the hands of Ashlee Evans-Smith, where Fox's muscle fatigue in later rounds gave Smith an advantage. After the fight, Smith observed, "I won because I hit harder, grappled better, had better ground techniques, cardio and leg strength."

The only dissenting medical professional I could find has no actual experience with transgender medicine, couldn't define transgender, and based his objections on claims that "all the evidence isn't in yet."