The surveillance video that Joel saw in the restaurant in Liushi was a work of Alice's.
John and Alice, and even other details in the video, such as the food on the table, were all created by Alice.
If a human were to create these "special effects", a lot of effort and technical skill would be required. Conversely, "face swapping" is the easiest and most realistic approach, but still, someone would have to "impersonate" John, and then replace the "captured face of John". The same applies to Alice's image, it needs someone to play the role - because Alice's actual presence cannot be captured on camera.
