Hi Dolus,
The figures you show there are the sort of thing that make statisticians exited. There is a clear trend towards the more recent the horse ran the better its chance of winning.
When trying to form a correlation myself in the past though I have to say that as your quoted research said there wasn't much to be gained from just looking at the days since a race. The only clear conclusion I came to was that the horse was at an advantage if it had raced in the last 6 days. I would suggest this is because it shows the horse to be fit and showing no ill effects from its last race.

KV