That's the first I've ever heard of Wolf's Head (sounds more like a microbrewery, lol).
I'm not seeing it on the MB approval list, so it may be one of those where the manufacturer says it is compatible, but you are really just taking their word for it.
Personally with something as particular (and expensive) as these transmissions, I'm more comfortable picking a fluid off of the official list.
This is really just not a place to pick something based on price, at least not to me. If it turns out Wolf's Head isn't compatible, it's not as though they're going to pay for your repairs or replacement.