The guidelines on gender identity are based on the BLP policies [1], which call for taking harm into account and not going into excess detail on someone's personal life.
Everything people are upset over in this thread is explained clearly in the BLP section on privacy, the gender identity section of the Manual of Style [2], and this essay on gender identity [3].
This particular example is completely clear-cut. Sources didn't cover them at all under any previous names because they're only known from one event. Someone who isn't transgender would be covered the exact same way. Wikipedia is an encyclopedia, not a gossip rag.
[1] https://en.wikipedia.org/wiki/Wikipedia:Biographies_of_livin...
[2] https://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style/Biog...