It doesn't look like retention of the shells is very good as when he pulls on them the belt doesn't move. Looks like any sort of tumble and the shells will fall out.
What if you want to load just one?
If you post a video of you throwing a couple across the room without any falling out and the same after someone rolls down a hill with them, I will be a believer. Until then, those look great... for three gun or other competition. I won't take them hunting or set them up for home defense though.