That's a fair design for a spring trap ,,now we just have to teach the guy building it how to lash something properly! He obviously has no clue. Proper lashing is Boy Scout 101,,,,
There are other things done wrong on it too .
The " spring" has nothing to keep it from sliding side ways off the tree at the butt end , the way it's tied.It should be lashed in 2 places to keep it from going side to side and it's nowhere near tight enough. Plus he used birch which will take a set very quickly leaving no real spring power after a very short while,, hard hack ,oak, ash or many other types of wood would be a much better choice for the spring. The spikes are also to short and not enough of them with no barbs on them,,which would only injure something allowing it to get away . The trigger circle should be also be made of willow, birch,or even pine,, heat bent , not cold bent, other wise it will oval out and probably splinter, and not release correctly, which it's already evident as you can see in the video. Either heat bend it over a fire or boil it in water to make it pliable first , then make you're ring.
That design is close to what we saw in Nam that we called a "fly swatter", which worked the same way pretty much but swung horizontally. Overall a good design, but in this case, just a poor execution of it.
How do I know this won't work right you ask,,,I built a few in Nam close to this design which accounted for 2 of my confirmed when sappers were trying to sneak through the wire on our fire base,,,,,that's how.
The bear trap type and normal punji sake ones shown elsewhere were one's we saw allot in Nam in our area too.
Just don't get caught setting things like that,,around here you'd probably go to jail for doing it,,traps like that are highly regulated and you could get into a shit load of trouble by building one. For survival situations,,,hell ya.