This is not a reliable way of determining the advantage of trans athletes.
First, we need to determine what the parent population of "transwomen" is. Every transwoman of certain age range, or only those on hormone replacement therapy? Is there any minimum duration of therapy or maximum level of testosterone? Does it matter whether someone started medical transition before, during or after puberty?
How do we define the top level of female sports? There are over 200,000 women competing in NCAA sports at all three levels combined. There are no more than 40-50 trans women competing there. So that's like 0.02-0.025% of them. About 0.5-0.6% of people in ages 18-22 are transgender. So that's a significant underrepresentation. Do we count the number of athletes who make the NCAA championships, make the podium, or win titles? But then, the number of trans athletes who made the NCAA Swimming championships went from zero in 2021 to one in 2022 to zero again in 2023. So it went from underrepresentation to overrepresentation to underrepresentation again in the last three years.
Lia Thomas was nine seconds slower than Katie Ledecky's NCAA record in 500 yd free. Cece Telfer was five seconds slower than Muhammad and McLaughlin in 2019. Were they too fast to compete against women? No. But we already know they were way behind in the standings when they competed against men. Anyone can tell something is not right when a mediocre male athlete becomes a top female athlete.
However, how do we judge athletes who have never competed against men? Do we have any "basis" for comparison in those cases? How good is too good?
How about bio markers? What do we consider the "normal" female range? Within one standard deviation of the mean? Two standard deviations, or three standard deviations? Do we need to set different standards for different markers?