Bucks have been growling since god created deer. I'm surprised this hasn't come out before. I've heard deer make all kinds of insane noises. The growl is something I've heard as well.

What I will give you is that it's sad that they had to come out with a "specifically designed" call. You can do a growl with you regular grunt tube. I do it all the time. It works great, and I love it, but i've done it for a few years on my own, after my brother told me he tried calling like that and it worked. I've seen some good results.