I'm trying to figure out how to get detailed depth data (the raw data) from the front-facing camera on the iPhone X. Apple's docs suggest that AVDepthData will return this data, but I've not be able to confirm this.
Is this the correct property to use to access that data?
Yes. The WWDC 2017 session "Capturing Depth in iPhone Photography" (https://developer.apple.com/videos/play/wwdc2017/507/) covers this for the dual-camera set up on the back, and it uses AVDepthData to return depth information. The TrueDepth camera uses the same protocol.