Part of it is down to the fact that most Japanese-style stick parts use circular shaped actuators that push against four small microswitched buttons which are centered around the stick in the neutral position. Whilst some sticks used bevelled actuators which compensate against this to a degree (don't think this is true of the V2 stick, though), when sliding the stick, for example, left or right whilst riding the bottom of the gate, it's actually a narrower part of the actuator which is interacting with the mircoswitch button than it would be if doing the same from a neutral starting point.
If you are moving directly diagonal from neutral, this is still true to a degree, but the microswitch will still hit the activation point part way through the movement.
The distances involved here are small enough that I personally don't tend to notice the difference, but I'm actually pretty cack-handed at this stuff.