They are told how many answers are correct.
But not which ones.
Let's draw this picture. I have 60 seconds. It takes me, let's say, 10 seconds to make my initial selection. Add a couple more for me to get back, because of my rather large body, and hit the buzzer. So I'm somewhere between 46-48 seconds. Realistically 46.
I only have two right. So now I've lost twelve seconds, and the clock is still running. It probably takes me another 10 to correct my mistakes, plus time to get there and back. Which should probably put me at about 22 seconds. You're asking me to be perfect this time, practically, because I'm likely not going to have enough time to win the car if I'm not. If I didn't get any new ones right, I have ten seconds. If I get one new answer I've got thirteen, which is not much of a cushion.
Do you see what you're creating here?