I'm not fully aware why the original Fender pups were placed in that original position, whether 'scientific' exploration or simply experimenting with different sounds from different placement along the body.
On my self build I generally unless requested, prefer a closer positioning of jazz pickups than Fender and slightly closer to the foot of the bridge. I also bring the P pickup closer to the bridge. Look at Dingwall model with 3 pickups, looks a little overkill but it likely gets all of the Fender type pickup areas covered. The further forward/towards the neck the pickup is, the less 'attack/tightness' string sound is detected whereas nearer the bridge more attack but less 'body', hence two pickups (or 3!) better than one. I also sometimes angle my jazz pups so theres another different look to consider eh?