The original article has Sci-Fi.
One of the intentions is to distinguish it from futuristic fiction which is more about the rip-roaring adventure than the science. For example, Star Wars would be labelled sci-fi, 2001 would be labelled SF.
If you're thinking it sounds like there's an element of snobbishness in there, you are definitely right. It's much the same as with those authors who prefer to say that they write speculative fiction rather than science fiction (SF as an abbreviation also has the advantage that it works for both of those).
> It must have something to do with the perceived audience for SF being young men (presumably unacquainted with women or why would they have time to read SF?). Olden time authors also tended to have firm notions as to what kind of story might be genre-appropriate: if SF is about scientists inventing things, or can-do he-men having adventures, well, that’s not what women do.
10% of the comments to the article use "SF" or "SFF" (for Science Fiction & Fantasy)
https://en.wikipedia.org/wiki/Science_fiction attests that "SF" use dates from at least the 1970s, eg. "The earliest organized fandom online was the SF Lovers community, originally a mailing list in the late 1970s with a text archive file that was updated regularly."\
Thus, "SF" is neither a new use nor an unusual use.