Except it's not. What's the opposite of "live"? "Prerecorded"?
So these Live photos are supposedly not prerecoded - except they actually are. They are a prerecorded video that you send to someone. There is nothing live about it.
It’s “live” as in “alive” because you get a bit of motion. The opposite would be “inanimate”, which seems apropos.
You’re right that there’s probably a video format under the hood but the experience to meant to be closer to a still picture with a bit of added magic (a la Harry Potter). The clip is too short to catch much action or have (intentionally) meaningful audio.