It must be a bear to keep clean. It just looks high maintenance and not particularly interesting. It probably is designed for a very specific audience.
A knife is a really bad way to access a camera bag, which is why thieves really don't do that. At a minimum, the knife has to cut through two layers of nylon and a layer of padding. And you are going to have to steady the bag to make the cut. Most people would notice that. Knives are more used to cut neck and shoulder straps--backpacks just have too many straps. Like Matt, I am more worried about the usual way things are lifted: crimes of opportunity.
If only there was the perfect bag!
The closest I have come is a Mountainsmith Tour lumbar pack with a shoulder strap. I have owned this since 1990 (32 years!). It gives me two ways to carry it and a larger outside pocket for those things that can be random (those things you don't take all the time)--gloves, hats, snacks, glass case. But it also needs a camera system that works with it. It is great from my APS-C Fuji, but not my Pentax 645D. I need a backpack for the Pentax.
As far as backpacks go, I have only ever found one photo-specific bag that has worked. I find most climbing packs far more comfortable in the long haul as well as more flexible. The suspension system, if used properly, just carries weight better. If you are out all day or working multiple days, managing physical stress is really important to maintain energy to shoot. The bag I have had for about 9 years is the Osprey Farpoint 40. I also use it when flying with my Fujis too.
I think the problem with many photo-specific bags are they seem to be designed to look good in a showroom or catalogue. That is great if I am carrying my stuff from the house to the trunk of the car. But the real test is whether I can use it to shoot (not just carry my gear) all day.
Now we just need to solve the problem of getting older...