Yes how could anyone say they put CPU in replays? You can tell a difference between CPU and a real person after a couple second into the replay. CPU doesn't tend to repeat moves when they miss, regular players do, one of the more obvious point. Other things you can notice is that player would go after ones with high %, etc.
Replay is better than watching them live, why? Because the spectator will add more lag to the already laggy game. And would you want to watch a laggy game with freeze frame here and there? or rather they saved it and give you back a smooth replay? That's a smart move on their part.