This is Chad Belding, he was a member of Fred Zinks staff. Chad and his Brother Clay did do the majority of the DVD Devil dogs for Zink.
I rather like that DVD, the calls they are using are basically duck call inserts, and yes this does work, you can do distress as well as howl with them. If you would like to test this, take a single reed duck call, pull the insert out, then run it like an open reed distress.
The howler is basically a short reed goose insert with regular short reed guts. Again, this works as well, take your short reed apart and try it, you may need to tune it to find the sweet spot, but you can actually get some good sounds from this setup.
I haven't seen the show, I have seen his FOWL LIFE waterfowling show and he has gotten extremely commercial since leaving Zink. It does get old pretty fast.
But, he has to bring in the cheddar just like the rest of us.
Now that he isn't working for Zink and has his own call company, Zink has dropped his predator call line, and I don't know if Chad is still using them, or if he is going to create his own line. His call company "Banded Calls," is just duck and goose calls at this moment.
Don't work for him, I'm just a duck and goose guy mostly, so I may know a bit more than others here. Chad and his brother have been predator killing for quite a long while, don't know that I'd call them amateurs, sounds like his show is doing a good job of making them look that way though. The Devil Dogs DVD is good, they do shoot one at close range with a 50BMG in the end, but they hunt from Canada through the US to Mexico, I have no qualms about recommending it.
Good luck hunting to you gentleman