I didn't write the article...it's just a literature review 
There are issues with studies about breed and biting, the huge one is breed identification, which isn't a huge surprise given that I've been asked if my dog is, a black lab, a Doberman, a mastiff and I'm often asked if he's a cross of his actual breed, but also some fairly random ones.
For the record, I own a Rottweiler, a very very typical looking one and I'd have thought an identifiable enough breed that I'd never be asked if the Black and Tan dog was a lab, never mind more than once, lol.
The general public are not good at breed identification.
You've also got that small dogs are always going to be under represented because they've done less damage and various other issues like that.
So when studies add up to overall breed isn't a major factor even with stuff like that going on - I believe it.
Looking at other sources of information, media reporting is really biased, they have an agenda, over here you get things like staffy pictures being the stock photo for dog attack stories even when there's not one involved and in America you get papers running for days with a story about a pitbull killing a child when it was in fact a lab retriever cross.
They've done studies about what the most prevalent correlations are in serious incidents and breed wasn't up there as a high risk, things like dogs not being treated as a family pet, the owner not being present and unpredictable/vulnerable victims were the biggest risk factors.
I have no clue how fostering works...but I'd want more information if you can't meet him, given that he's going to have to fit in to a family and with existing dogs, but his breed wouldn't bother me in the slightest.