Why is it important if the dog has a mechanism that locks the jaw, the point is they just don't want to let go, that's the way they've been bred.
Part of Australias' sordid past that no-one speaks of includes dog fighting where the dogs fought sometimes to the death, I had the misfortune to attend 1 such event and it wasn't long after the jeep bloodline gained a following in this country.
The two sickening displays I witnessed involved pit bulls of the said bloodlines pitched against a Rottweiler and the other against a staffordshire. The pitbulls won both events and killed the competitors and remained clamped to the dead dogs well after they died and in 1 case it took almost 5 minutes to remove the winning dog.
The owner of one pit bull had tyre levers (for a car) to pry his dogs off and had to lend the levers to the other owner to remove his dog from the dead dog.
In my district pit bulls are the the dog of choice for drug dealers and they are trained to be savage, they are deliberately not socialised to enhance their protective qualities.
I don't trust them because I've seen what they are capable of.
Responsible dog owners are rare where I come from (and most places I've lived) so I don't think any bozo should be able to buy something that could easily kill a child and just shove it in the back yard.