Seems more like rules state everyone but cisgender men in the way they worded it. Trans-man would be included since it says anyone under the trans umbrella.
Women only… trans women are women, and transphobic or gender critical talk isn’t allowed. Anyone under the trans umbrella (eg non binary) is welcome
I googled but could not find source. I only found more memes based on this graph. Which isn't to say it's fake, could simply be in some research paper hidden away under a paywall. 15k sample is a very big study though.
The graph alone is highly problematic to make any argument though as it doesn't specify other critical axis such as age which would highly change the meaning of this graph. The older you are, T levels fall, but your IQ increases. So age alone can potentially explain the phenomenon we're seeing here.
My attempt to find the graph only resulted in many counter points, however.