I think that is should be quite easy to understand what can considered as pizza and what is simply not acceptable. Last year we saw some entries that were not pizza, some them were not even cooked. As long as you have a cooked dough you should be fine.
Clearly formulated conditions of the competition will help avoid different interpretations of these very conditions.Then it was easier to immediately write like this:
- I reserve the right to ignore any participant for any reason.
We are all adults, if you go to a restaurant and ask for a pizza I'm pretty sure you don't expect to receive a cold plate with some random ingredients, don't you?
In different countries, on plates you will see completely different pastries disguised as pizza (to the horror of the Italians). 
Therefore, specifically stated conditions are the key to the transparency of the competition.