There are many occasions when an attacker will try to hit you with something and if you already had deployed your knife and moving around,
you might avoid the hit but it gets your knife on the back of the blade, therefore if the lock failed this test it may as well leave you with no weapon in your hand.
So it's not nothing. It shows that this particular model/design simply fails one of the requirements to be a weapon, that's it. Many "tactical" knifes will fail this test...
When designed with different priorities other to be a weapon, knife locks will fail even if you hold the knife over the lock and someone give you a whack on the back of the blade...
Knifes that are designed well to be a weapon will most likely not fail.
I did this with few inexpensive folders - the small Rat2, Zancudo and Heiho, and Heiho was the only one that even (with LAWKS not engaged) when lock failing during the hit, the assist spring will lock it back immediately.
The Zancudo will fail even with light hit, but again - when steady pressure is applied, it will hold perfectly. The Zancudo is simply designed as something else, other than a weapon, same as Rat knife. Of course you can use them as one if you need to but you should consider the consequences...
http://www.youtube.com/watch?v=7Dx5Ub5eFNA