I could almost go along with the idea but then I think of how often my active AF points are not in the centre. Mind you with a DSLR the furthest points are not exactly at the edge, but parts of the subject certainly are. What do you think?
I agree. If there is significant vignetting (sometimes hidden by in-camera software) it can affect the amount of light/contrast available for the AF. Though this will probably be more important for RF lenses where AF points go almost to the edge.