Group-Area Af in AF-S

On p. 550 of Mastering the Nikon D500, while discussing Group Area Af, Darrell Youngr states that in AF-S with matrix metering, the "camera will detect human faces in the viewfinder". Does this mean the METER will take its reading off the face or that the FOCUS POINT will be the face?
This is really important for me to clarify. Thanks for any help.

Providing face priority mode is turned "On" when choosing an AF area mode in the menu the camera will give priority to faces and can detect up to 35 at a time always giving priority to the face nearest the camera.
The camera will detect the face and focus on it - it will still use matrix metering to measure the whole scene for exposure.
It does work well and I have used it for some model shoots without issues.
Good luck.