When people are not in front of you, people are much faster to complain and dislike.
Thus when this guy sold a sub-optimal pizza in his shop to a person in a hurry, they would rather have the food and not start a verbal fight. But when they are physically removed - they are free to look at the quality and make a complaint.
PS: Customers aren't paying for your mistakes, your profits suffer. I just recently sold off a bunch of excess sports masks(it's faster to order a bulk package from a Chinese manufacturer, than buy one). I sold them off on eBay at cost and people bitched to me about the fact that the postman didn't come on time... while not paying for expedited delivery. In the end I lost $10.
For instance, the widget that I make, I screw up a small number of them during production, and I consider that to be part of my cost-of-goods. The rare customer with a complaint gets a full refund. My overall profit more than covers the occasional mistake.
Some other things that the big retailers do is simply not to sell goods that are open to dispute. Home Depot would look at making a pizza by hand from scratch at a retail location and delivering it to your door, as some kind of crazy.
Simply handling disputes is enough to bury any retailer who doesn't learn how to handle it. If it doesn't consume their money, it will consume their time.
I have a very small side business, and have handled the above needs by working exclusively through PayPal. Also, I have enough of a mark-up to cover disputes. It's kind of ironic, but to survive in business, you have to be comfortable with somehow letting your customers pay for your mistakes.