You should read up on what happened in Connecticut to understand why this became a problem. It’s the biggest example of the concern over MtF women training as male with the advantages of male biology and then becoming female and using those advantages in female sports. Two MtF women in Connecticut did just that. They joined a female high school track team and proceeded to absolutely smoke every single girl on the field while destroying several Connecticut high school state track and field records and winning every state championship. That is not fair to the girls who were born biologically female and didn’t have those advantages in training. Connecticut basically told the biological females tough shit you don’t have a choice which wasn’t the way to handle it.