Swyers disease. https://en.wikipedia.org/wiki/XY_gonadal_dysgenesis
A Genetically-born XY person with fully developed female-organs and no visible male-organs hence failed to go through male-puberty remaining for all intents and purposes female-adjacent.
The Olympics committee via Scientific investigation have determined that Swyers disease persons are essentially female from birth including physical characteristics hence an exception has been made to be allowed in the Olympics female category for participation.
Trans-persons are still not allowed in the Olympics female category no exceptions.
https://www.bbc.com/news/articles/crlr8gp813ko seems to have a good explanation. In short, it’s complicated, and the IOC drew their lines.