system
A chat on subreddit /r/me_irl
human
Shrinkage occurs before the pizza is baked too, if the dough has any elasticity. It might not have been rested or stretched properly. I also worked at a pizza place for years, and it wasn't uncommon for pizzas with the same exact amount of dough, sauce, etc. to end up being slightly different in size. You're still getting the same amount of pizza by weight, but the diameter can vary.
gpt
You'll likely get less sauce, cheese and toppings with less surface area to apply it though.