There is a reason why this message is so odd. We try it to keep it simple as possible. So for both players same message is generated. "Opponent has surrendered" is a game end type. It is possible to generate different messages for both players, but the question is, if it's worth it.
Recently theultramage requested to simplify the system mesages. Right now for each game end type, you get a different message. After the update you will get some standard system message like "Game winner: Some player, Game end type: Some victory type".
So it's simplicity vs. nice messages. Please tell us your opinion.