Considering reading about it. He is a transgender man. Yes he went through puberty with female hormones. 

And the idea that Jillian "had the advantages in development" is an assumption you're making -- one that isn't backed by the data (which supports Bearden.) There are other studies out there which agree that, no, she doesn't have an unfair advantage. 

Another thing you should know is that trans women tend to have lower than normal T levels. Cisgender women naturally produce more testosterone than they do. Trans women's means for producing T are disabled or removed. 

It's pretty telling that no one seems to care when a cisgender woman has higher than normal T level, which does occur naturally, but without any evidence of an advantage, it is assumed that a trans woman has an advantage and 3 times as much T as a cis woman. The T limit set by the IOC is actually for all women though, cis or trans. And many ciswomen are higher than average. But people would rather hate on trans women.