I know there are few users that forgot to take picture of their pizza with their username, but they still upload the process and I don't see anything suspicious like (the pizza is different, the background changed etc). So, I think they're really forgot, not cheating or something like that.
After all, if the winners already announced, anyone can going back to the thread and check whether the entry is valid or not.
FYI, there are 13 pizzas excluded, those pizzas might be AI generated, not a pizza, not a valid entry etc.