Is it just me or does the depth map also include color/brightness? The vatograph images shown seem to also be mostly about subject recognition, not depth. How accurate are these inferred depth maps?

It's not accurate at all. Measuring accuracy would require some sort of calibration. If this was using some kind of stereographical setup or lidar data to calibrate the inferred depth could probably be calibrated, but this is not the case.

Not to say it's useless, its perfect for subject isolation and it would be very difficult for someone to tell the difference with a scientifically accurate equivalent