Widow Maker hack squat. Looks like some dangerous bullshit. 
Considering Justin Harris can do 405 for twenty (look it up on YouTube, probably another vid you can select from the one in your post too), and here he is doing a measly 135 on a Hack Squat machine, I doubt his knees or back are stressed too much.
Tom Platz used to do this version as well. Milos is an advocate of them, and I happen to like them too. But even though you've never heard of me, the first two guys happen to have some of the best pairs of legs in the business.