1. There is still a convention bounce in there for Kamala, as I understand it. It's small, but it's present. So maybe Trump would be doing 5% worse if not for that.
2. More importantly, the model is designed to do exactly this. I don't think I need to go through a hypo for you, but I'll do so for the sake of the general reading population.
Suppose there's a presidential race, and one candidate is winning by 10 points in February. What are the odds that the candidate will win the election? If you go by the polls alone, probably close to 100%. It would take a massive polling error to make up 10 points, even with the EC. But it's still Feb, which means a lot can change. I would guess that the model would give about a 70% chance for the winning candidate to win -- the other 30% being uncertainty about what will happen in the future.
Now, over time, the polls do narrow a bit, but on November 1, the leading candidate is still up 6. The odds of that candidate winning the election would be much higher, like 90%+. The reduced uncertainty more than compensates for the reduced poll margin. At this point, really the only thing the losing candidate can hope for is a really pronounced EC effect or a large polling error.
3. In a way, this is a lot like pricing stock options. A 1-Y call option with a strike price of 50 for a stock trading at 40 will usually trade for more than a 1-mo option with a strike price of 45, even though it's less favorable on its own terms. The time to maturity makes a huge difference.