@crispbuttyfan
From what I know about this most trans women testosterone on hrt is aimed for and kept to less than 3 nmol, and would very rarely be as high as 10, unless the hrt wasn't achieving the aim.
It is in fact usually less than cis women.
The aim according to one of the latest studies on transwomen on testosterone suppressant is to achieve a level below 3.5 nmol/l. The average range for healthy adult women is 0.5 nmol/l to just below 2.5 nmol/l.
According to one of the first longer term studies (up to 3.5 yrs on testosterone suppressant), the most successful results were in patients who achieved 0.75nmol/l, which is within the normal female range but not below and according to this study 75% of transwomen did not achieve the desired result, and they didn't even get close to the female range.
Therefore your claim that transwomen "usually" achieve a level of testosterone lower than women is false. Unless your claim is based on a different study?
But even if your claim was true, the IOC has decided on a level of 10nmol/l which is of course at least four times higher than the average healthy woman (even women with Polycystic Ovarian Syndrome only reach 6nmol/l).
And while intersex conditions like Caster Semyana's are extremely rare and the advantage testosterone gives her over the other woman was plain to see for everyone, she is a woman and making allowances for a woman, however advantaged her body makes her is different from allowing male-born people to compete with women.
And as for the general advantage of a male physique over a female physique, the changes resulting from suppressing testosterone that you describe as eroding these advantages would take 15 years according to medical researchers. Given the short duration of most sporting careers, this means an average transwomen continuously suppressing testosterone would be retired before losing that male body advantage.
Here are some of the advantages that remain: larger lung capacity, bigger size, more powerful heart (due to its larger size), larger muscle mass due to increased numbers of myonuclei (muscle fibres) and a larger skeletal muscle fibre area , better muscle memory, longer reach, higher grip strength, better oxygenation of muscles due to increased haemoglobin, faster recovery etc etc - none of these are lost within the short amount of time stipulated by the IOC.
On 10nmol/l their three to four times higher testosterone levels also give transwomen a boost in speed and performance in addition to their other physiological advantages.
So get transwomen involved in community sports by all means. But keep them out of competitive women's sports or admit that you consider the desire of male-born people to excel against female-born people as more important than fair competition.