The game creation mechanism is planned for redeisign (ever since the messages were added). There are few deifferences to the current system.
Right now, when challenge is sent an "incomplete" game is created (lacking opponent's name and deck). If the opponent accepts, this information is added and game begins. If he rejects the game is deleted.
This will be replaced with message-based mechanism. A challenge message (also containing new "challenge text") will be sent to the opponent. If he accepts, only then a game will be created.
We have the current system due to historical reasons - we had no message system back then.
Since the challenges will be transformed into message like form, the left part of the "challenges" section will be modified as well (sorting, filters). It will be very similiar to message part (the right part of the "challenges" section). You will have something like "inbox" - all incoming challenges and something like "sent mail" where all sent (outgoing) challenges will be listed, ready to be easily managed.
Also "challenge text" will be added to the challenge message, for opponent to read. "Accept if you DARE" for example ;)