Stablize/AltHold Indoors == Stable Hover?

I see videos on DJI drones and other cheap drones just hover indoors without moving around, assuming you aren’t touching the controls. Obviously no GPS at this point.

What are the knobs that need to be turned to get a drone running Ardupilot to run this well? I’m assuming very refined harmonic notches and great PIDs? Is there more?

DJI uses optical flow sensors for indoor position hold:

Okay that makes sense! Thank you.