It's common knowledge there are server emulators that you can mess around with (every old MMO has one). The reason your character moves x6 faster at "max speed" is due to the internal speed variable being 1 byte long, giving a max value of 255. 255/40 (retail speed) = 6 times, which at least feels a lot faster than ARR's speed on Chocobos.
Going through some of the old zones you can see the size difference from the time it takes to go from the two ends, while running at the speed of a car.
What "facts" are you stating other than your own opinion? Unless we get the actually length of the zone in the map files for both games, and they both use the same world coordinate system (so everything is in relation to each other), it's all opinions!