Yeah, it's like the difference between sitting in a stopped car with all the doors open vs sitting in a moving car with the front driver and rear passenger windows open. The first one might feel cooler on a windy day, if the wind is blowing in the right direction, but the other will have consistent airflow from the outside through the car and back outside.

you put it in front of the AC

Indeed, there's a reason we have all sorts of ducting, we want the air to flow specific ways. Not so great when hot air could easily recirculate immediately back to intake.