Obviously they're only giving one day for the download so that only the people that actually care about this download it. The rest of the people that bought BF3 on the PS3, but don't care about 1943, are gonna be left in the dark and aren't going to redeem their vouchers.
This way, EA appeases the people threatening to sue them, but at the lowest cost - Most likely, only the people that are suing them will have the knowledge required to download the game, while the rest of the people still don't get it. They're still not giving all BF3 owners on the PS3 their rightful copies of 1943.
They should keep suing them.