Also, when should this notification appear? The instant that they have a completed objective? That will get quite annoying to experienced players, who are most likely well aware that they completed an objective. Also, there is definitely strategy involved in when
to reveal that certain objectives are done.
Does the message appear in the log? If so, then it reveals information to other players that shouldn't be revealed. "Player XX has an objective card they can reveal" If we were supposed to know what other player's objectives were, we wouldn't see just the backs of their cards.
Having people not rushing to the end of a game is not a serious situation. If the two players are happy, that's the point of the game. If there was a third person involved who knew the interface, they got the win. No problems.