They definitely growl.
I've heard Mishka growl twice. Once when my friend was visiting with a dog. A few moments after they left and I was sitting on the bed with Mishka comforting him - the doorbell rank. He jumped up and let out the deepest meanest GRRRRRRRRRROWL... I could not believe it.

And recently I heard Mishka growl when he was having his shrimp and Bean approached too close!!!