I think that is kind of the point. The out-of-place x, by its very incongruousness, calls attention to and centers the LGBTQ constituent. You see it even with English words of Germanic origin, like spelling "folks" as "folx" or "women" as "womxn".
Edit: Wikipedia traces "womxn" back to the 1970s, but it seems unlike "womyn" it didn't get much currency in ordinary feminist usage, only finding purchase when the queer angle was added.