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.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?