I suspect you're correct - but I would also add it potentially depends on the sport in question and whether self-identification is the pre-requisite for involvement. Sport encompasses such a wide breadth of activities and games that it would be difficult to make a universal judgement on fairness without considering the specific nature of what is being asked of the athletes. It may depend, for example, on whether it is a direct one-on-one competition around a single skillset in which biology may play a crucial advantage (such as weightlifting) or whether there is no obvious biological advantage (snooker) or whether the sport in question relies on varied skillsets amongst multiple people (such as hockey or basketball).

I don't think it's necessarily just about testosterone either, there are specific advantages and disadvantages that come with other aspects of being human. I think on this one we should defer to the experts in the fullness of time. I also don't think it's necessarily all about testosterone.

And yes, I agree the majority of people aren't transitioning to get ahead in athletics... and those trans-athletes who do transition aren't necessarily doing so to get ahead. That doesn't negate the issues created though - and I think we do trans-people a disservice by pretending the top tier of athletics can be managed in exactly the same way as transitioning within the bellcurve of chubby and lazy society (where I live). Inclusion can be a goal but it doesn't have to be an absolute - and the fairness issue is clearly a sticking point for some (mostly cis-female) athletes. It needs unpacking and it needs unpacking with science and without feelings. :o)