Is symmetry between left and right brain what allows consciousness to exist?
The symmetry between right and left brain doesn't really correspond to the types of symmetries they're talking about in the article. They're usually expressed as "The laws of physics are independent of X; you can substitute X with Y and the laws work the same." There isn't any kind of substitution here, so no place to apply the symmetry.
It's literally a medical procedure that children (or adults[1]) with extreme seizures or epilepsy undergo so that they can live more normal lives.