Just some insight from a Greek American. The deserts 'on the house' are a custom that most people visiting Greece don't expect. Nearly all restaurants do something similar. It's called a 'kerasma'. It's basically a departing gift, and a thank you for eating at our establishment. It can be a plate of fruit, a desert with a shot glass of traditional liqour, etc. It's a nice touch, but it's a common tradition, once you ask for the bill. So asking for the check isn't the end of your meal, it's the entry into the final act of your meal.
