Topic on Talk:Gender neutral language in Spanish

Could anyone link a source that references this? In the "letter substitution" section, it says "Note that, unlike English coinages such as "princex," which is only for people of color, a neutral x in Spanish is not only for people of color. "Ellx" can be used by white people as well." I have never seen this limitation for princex and similar coinages in English and want to have a source that explains this further.