So quite literally, by the rules set by the IOC, inter gender or mixed gender athletes are allows to compete against females, while their blood contains more than double the allowed level of testosterone females have. How's this fair
It's not fair and there are other advantages too, things like height in basketball.
Sports need to be separated by biological sex not gender identity, if there's lots of demand for the inclusion of DSD and trans people though then that can be facilitated with separate events just as we already run in the Paralympics.