This article does not say he did not have surgery. While this article quotes a layman stating it wasn't 'resectable', other articles state they were not able to remove the tumor completely due to its shape. You don't need all of the tumor to produce -L.
"Officially they had to do a biopsy to determine it was a glioblastoma, but when it's in a butterfly shape -- already in both hemispheres of the brain -- it is almost always a glio and it is impossible to fully resect without coming out of the surgery "different.""
Biopsy: A biopsy is a medical procedure to remove cells, tissue, or fluid for lab examination