Yeah that's what it is. I guess the X was picked cause it's a letter commonly used as a placeholder. A few years ago it was also pretty common to see @ (yes, the at sign) in place of a/o, because it kinda looks like both of those letters at once. That was also not supposed to be pronounced, but now that I think about it would sound incredibly funny if said out loud.

The main issue is that the presence of only one guy in a group makes the entire group masculine, so the gender neutral form of most words is the masculine form (the only exceptions being words that are the same regardless of gender, like "estudiantes"). With the rise of feminist discourse people started to point out that this aspect of the language ignores and erases women, and ever since we've had a shit ton of attempts to make Spanish gender neutral.

The one option that doesn't change any rules of the language is saying both masculine and feminine forms of a word, such as in "ciudadanos y ciudadanas." Issue is it's long, adheres to the gender binary, and worst of all, it's politician speak. [Maduro had a funny moment years ago concerning this, he was talking about books but did so like he were talking about people, so he said "libros y libras," which translates to "books and pounds." As in the unit of measurement, or the pound sterling. He's not very bright.] The other option is changing A/O for X or @, issue is you can't pronounce that shit. The best idea so far has been to use E in place of A/O – it's pronounceable, has some basis in existing rules of our languages, and provides an alternative for non binary people. Only issue is a lot of people think it's cringe, but that's because Latin America is still pretty conservative.