hi,
I asked exactly the same question when I got my bayraider expedition.
the amount of play in both centreboard and rudder doesn't fit with the build quality of the rest of the boat. so I assumed it must be for a reason.
A friend of mine was regularly having to go snorkelling to free his swing keel after it jammed with stones (not a swallow yacht). I wondered if the amount of play in the centreboard was to stop this happening, although I haven't been able to confirm this I've left mine as it is for now.
Look for some earlier threads on this topic, I think some people have put shims in to reduce the movement.