That's what I thought when I first came up with the card, but the more I mull it over, the more balanced I think it is.
Remember, the scoring modifier applies to everyone, so to gain a significant points advantage from it, your deck needs to be significantly different. And the knowledge that this is going to occur is in front of players from the beginning of the game, so it challenges certain dynamics of deck building.
Normally, winning the Governor split 7-3 is GG. With this, it still might be, but you have to win by more than a Province for it to count.
And if the strategies are similarly competitive to the point that the Delusion points are the deciding factor, ending the game on your turn is still probably part of your win condition, but you're trying to engineer a 1-pt loss instead of a win.
I'm actually super interested to try this out.