That seems very counter intuitive to me - if you are spot metering and move the focus point to the eye, Canon mid-range cameras (?) still spot meter off the center of the grid. I would think this means you should be mindful of light/shadow changes between the center and the selected eye.
I believe he said certain of Canon's top models can meter off of the AF point?? He was unsure whether the R5 II would be able to meter off of the selected AF point or not?
As i mentioned, in evaluative (matrix) metering there is weight given to the confirmed AF point but in context of what the whole scene is doing. It's not that they can't do it with the spot meter, they must think doing it in the center is better. I think the canon logic is the spot meter is a measuring tool to judge exposure rather than always wanting the spot under the focus point to be the average exposure for the whole scene. Of course there is also EC.