time alignment Q ears or center of both eyes

I have learned to set time alignment a few different ways as a result of this site (physical TA, flip phase technique, listen for warble, etc), but I have always wondered the rationales for why some say when making physical measurements you measure the left channel to your left ear and the right to the right while others say you measure both channels to the center of your eyes.

Can anyone answer in your opinion why one is more/less correct than the other? Just curious.