English is not my native language, but to me charred is a type of burned?
It was partly a joke, it's somewhat of a touchy subject for those that love New Haven style pizza. People that don't care for that style often called it burned, and fans of new haven style pizza are quick to "correct" them.
With a coal fired pizza, the goal is to get a bit of black on the outside, a crispy crust with a fluffy inside.
Some places with a high heat brick oven will char a pizza. I like a pizza "well done" because a few burnt spots on the crust and topping is worth the extra crunchy crispy crust