I only have real life experience with three pit bull attacks. Two was children, totally unprovoked and unexpected. The third was my own attack, which ended with a dead dog.
I know for a fact that all three were indeed pit bulls, not mutts.
So that's what I base my opinions on.
I've seen other dogs bite, sure. My bird dog has bitten a couple of people. But there's a big difference between a bite and a deadly attack.