I have a friend that was an instructor for the Marine corps equivalent, a contractor for blackwater, and is a cop now-- and he trains the other cops in this and the nitty gritty gun shit, trains swat teams or something like that. His brother is a black belt and one of my old coaches.
Anyway, he's a blue belt I think. Last time I trained with him, it wasn't really even worth sparring with him, I'm years ahead. We spent more time with me showing him stuff and letting him drill on me.
Will it toughen you up? Yeah. Is it the same level as you'll get in real BJJ? Not even close.
There's a video of Paddy Pimblett rolling with these guys, and he's effortlessly destroying them.
I still think there's value in it. It's not going to have anywhere near the technical nuance and attention to detail you'll get from actually training or probably just spending the same money on an instructional from a legit grappler.
If you're already a good grappler, it's probably mostly a waste of time, although I imagine there might be a nice nugget or two in there. You never know, those military guys are smart, and know how to survive.
So I think the answer just comes down to your goals. Do you want to be a competitor? Or do you want to have a more general education?