A Question about Fannish Terminology

sholio wrote an essay just recently about why Steve/Bucky AUs don't work for her (the AU part, not the Steve/Bucky part) and quite apart from the contents of the essay, it got me wondering about what we call AUs in fandom currently.  Back when I got started, *crotchety old fan voice* things like high school AUs and coffee shop AUs were called "ARs", or Alternate Reality fics whereas  "AU" referred more broadly to both ARs and also "what if" stories.  However, sholio only talked about AR-style AUs, and a number of her points don't really work for what if AUs.  A while back, I ran an Avatar: the Last Airbender AU meme, and after getting almost exclusively AR prompts (and most of those for fusions) I had to explain that what if prompts were definitely also accepted.  I periodically see meta about how the writer of said meta doesn't think AUs are enough like canon, then goes on to describe only AR-style AUs.

Did the meaning of AU narrow  and I didn't realize it? I would kind of like to know, most of what I write other than drabbles are what-ifs.  What if Lupin bit Snape when they were in school, what if Azula captured Zuko at the beginning of  "The Southern Raiders," what if Iroh died when he drank white jade tea. The story I'm working on right now is a what if: what if those Earth Kingdom soldiers in Book One had managed to capture Iroh and Zuko and take them to Ba Sing Se.  If these aren't AUs, I kind of would like to know what to call them.