I agree, though some fandoms wouldn't bother to call the latter AU; it often depends how much of their corpus tends that way, anyway.

Fanlore gives examples of AU, including:

The most strictly defined AUs may diverge from their source canons in a single specific way (for example, a Star Wars AU in which the first Death Star is not destroyed, a Merlin AU in which Merlin comes to Camelot as an agent of Nimueh, or a Castle AU in which Johanna Beckett was not murdered). More broadly, an AU may transplant a given source work's characters to a radically different setting, shift the genre in which their adventures occur, and/or alter their professions and goals, such as those popularized in the Xena: Warrior Princess "Uber" genre.

There's some fascinating taxonomies in that article.