AC is generally a lot cooler, even at higher temperatures. After 15 minutes, the cabin may also be sufficiently warm.
Remember, it's aiming to keep the temperature of the cabin at 19 degrees. That doesn't necessarily mean that the air coming out of the fans is that temperature.
The sun can also effect the climate control. Even if you have it set to 22 and it's 3 outside but really sunny, the car has a sensor on the dash to sense that. So you'll feel a lot warmer than it actually is, therefore cold air comes out.
The best way to test it is to set it to HI with AC off (Econ light on).