That's an interesting stat because in my computerised system I take no account of finishing position in past races merely lengths from the winner. This would mean that a horse running 3rd at 0.5L would get a much better past rating than a horse running second at 3L. Your figures show there isn't a huge amount of difference.
The comments made by other posters was prompting me to do a little research on this one and this reinforces it.

KV