I fully agree with the addition that personal interaction can make waiting for 15 minutes acceptable if a reasonable explanation is given. I can accept that something has gone wrong if somebody feels responsible and apologizes for the mishap. It might even develop into an occasion for a welcome chat with restaurant staff. For instance, I recently visited a newly opened restaurant at its 2nd day where we had to wait for the food very long. The server apologized and talked about the challenges they've encountered, and gave us a free soup with bread. This can still be annoying if you are in a hurry. However, we were not and so it gave us the opportunity to get in touch with the new staff, increasing the likelihood of us going back there.

In a non-personal QR code setup, on the other hand, responsibility is shifted to some bureaucratic process which is nothing but frustrating.

As noted in the article, most/many people do not go out for diner to quickly buy and consume a meal, but to spend nice time with people. 15 minutes waiting time spent chatting with a waiter or with each other even has the potential to contribute to a positive experience, whereas 15 minutes setting up your smartphone definitely does not.