I can succinctly disprove your statement claiming there is no trans at S;G by providing you with a link that serves as irrefutable proof stating that at least Ruka is a transgender woman.

Kurisu has a page implying she may also be a transgender woman as well.

https://lgbtqia-characters.fandom.com/wiki/Makise_Kurisu

Ruka UrushibaraLGBT Characters Wikia