I would guess by the amount of people who recieved this game on launch day and even the day before that not many retailers took notice of any policy. It would surely be impossible to do release day delivery if they couldn't post until Monday night.
No, I believe all retailers did adhere to the policy, it's one of Activisions rules, otherwise they wouldn't be allowed to sell the game.
The majority of games would have been received, but Royal Mail 1st Class isn't guaranteed next day, so that's why people might not have got them. E-Retailers needs to be able to send the game out at least two days before...
For example, my copy of Assassins Creed Revelations from Shopto has shipped today, which means it might come Monday, but I will defiantly have it for release day on Tuesday. If it ships Monday, that is less so.