I imagine, wether its the primary reason or not, the salmonella concern is also a part of why they aren't allowed.
Looking beyond it being an actual risk or not, they are clearly paranoid about it since they don't allow cats/dogs eating raw diets to be certified for this reason.
I think that's overly cautious in the majority of situations, but I can see why they would want to be careful with people who are at higher risk (in hospitals, nursing homes, etc). I'm sure it could be a big legal issue if someone did get sick.