It is definitely brindle.
Unfortunately, the media has take every dog that has Bulldog and Mastiff origins and has stuffed them under the all encompassing label of “Bull Mastiff”.
The correct term is actually “Bullmastiff” (one word), and they do not look like this dog. This dog looks much more like a Presa Canario or Fila Brasiliero to me.
He looks exactly like a mastiff to me, NOT a bullmastiff.
Tried to post the image, but that wouldn’t work for me right now...