Do you have personal experience with that, or is it a guesstimate?
I suspect that if the dog has a hold on a victim, pulling him like that might risk tearing larger wounds. Though it might cause the dog to let go of the victim, you might be its next victim.
Making the dog dead is the best bet, IMO.
I’m in no way an expert, but I have pulled apart four or five dog fights that way; the biggest dog was a boxer. I’ve never tried it on a pitbull.
All of the dogs were too surprised to turn around and snap at me, so I don’t know if it’s possible for them to reach you; as long as you can keep it moving sideays I think you’d be fine.