The extra bit of rest I refer to is not the time between putting them on w/hood and the first race. Darkness y/birds in the year of their birth moult, get trained, raced and then moult out again, a lot to put a young bird through. Pairing them that bit later gives them a bit more time to build up much needed reserves.
There's many ways to race w/hood. Since racing my y/birds on darkness I've found that pairing up later and sending them to the first race sitting 6-8 days on their second round benifits them in the long run. I take their hens away on the Thursday, let the cocks sit Thursday night and send the cocks Friday sitting, they're on w/hood from then on in.