I think in order for kevlar to be effective it has to be in multiple layers with the direction of the fabric alternating directions. I don't think Dupont would ever claim that one layer of kevlar is very effective.
The knives they were using did not appear sharp at all.
I will say that first test with the guy trying to pull the material apart is misleading. He asked the guy how much he can lift and he said 300 kilos. Problem is lifting and pulling something apart are two different muscle groups.
I was visiting my parents a few years back and my dad was given a sample of those pool covers that an elephant can walk on. It was one of the fabric tiles with a slit cut in it and they were giving them out to people to try and pull apart to show how strong they were.
I took one look at it, bent down, put my foot through the slit and then pulled up on the fabric (like I was trying to lift it) and it tore apart with relative ease.