Which camera focuses on Quad-Cam 64mp in Quad mode?

I have the quad-camera board and the four cameras i just got, and can use libcamera-still to do an autofocus (though for some reason in libcamera v 0.0.11 i can no longer use picamera2 in scripts?)

but im confused about the camera focusing. I know all the cameras are synced and whatever values get set for one affect them all. but when it is autofocusing, which camera is it looking at? (or is it averaging all the cameras?)