>the Apple APIs may not even use the 3D scanner, given that Animojis apparently work with the scanner covered up (and don’t work in the dark).

Animoji uses all of the front sensors - RGB and TrueDepth.

From https://www.imore.com/yes-animoji-uses-truedepth-camera-syst...:

> the TrueDepth camera system captures a crude depth mask with the IR system and then, in part using the Neural Engine Block on the A11 Bionic processor, persistently tracks and matches facial movement and expressions with the RGB camera.