Can I toss in the idea that one bite by a pit bull might cost you your arm, but one bite from a labrador retriever would likely not?

Sorry, but Fact. Not. That's an opinion, not evidence. A very small fraction of the population bred dogs for fighting. A somewhat larger percentage of the population got the dogs for the wrong reasons, didn't socialize them properly or didn't care for them at all, and attacks happen. But that can be said of any variety of dog that is ill-cared for (see the link at the bottom of the page. Chihuahua is the number 1 biting dog.) As a child I was bit by an old cranky cocker spaniel in a setting where they should have known better than to leave the dog loose in their front yard where a child would be tempted to try to make friends.

https://en.wikipedia.org/wiki/Terrier

Most terrier breeds were refined from the older purpose-bred dogs.

The gameness of the early hunting terriers was exploited by using them in sporting contests. Initially, terriers competed in events such as clearing a pit of rats. The dog that was fastest in killing all the rats won. In the eighteenth century some terriers were crossed with hounds to improve their hunting, and some with fighting dog breeds to "intensify tenacity and increase courage".[1] Some of the crosses with fighting dogs, Bull and Terrier crosses, were used in the blood sport of dog-fighting. Modern pet breeds such as the Miniature Bull Terrier are listed by the Fédération Cynologique Internationale (FCI) under Bull type terriers.[2]

My pit bull could clear out the rats in the garage, but so could my blue heeler. Both are (the pit since passed away) excellent pets.

https://www.caninejournal.com/dog-bite-statistics/