Unless you have actually lived with (that is interacting with the breed in your house everyday)you really cannot know how they are. I agree that breed specific assessments should be made. This is not the kind of stuff you can learn at university, it comes from everyday interactions with the dogs. Just like there are General Practitioner doctors, but then there are specialists as well. I know alot about dogs in general, but do not know pitbulls specifically, I am a Husky/Wolf/Mal specialist. I would probably not trust the opinion of a General Practioner assessor to assess a potentially "unadoptable" Husky/Wolf/Mal. I have lived with them, in my house, for many years and can spot their ultimate potential, they are not for everyone but they are ALL adoptable to the right committed situation.
The dogs at the shelters need to socialize more with the other dogs and people, isolation is a death sentence. Breed specific assessors should be implemented into the system.