Not sure if that's standard - I was mailed mine within days of the match and asked to have it back within a short period of time. I would suspect this to be the standard - after all, without a contract programs aren't really sure a candidate will show up come orientation time. I'd hate to be the PD two weeks before residency starts with some no-shows (it can still happen of course, but having a signed contract beforehand would make it less likely IMHO).