So this is more a reply to the very original question as opposed to where it has strayed.
One of the tasks my dog does is what I call "Cover Me." When I am anxious or feeling threatened by a person, he moves in front of me and either stands or sits between me and that person. It is completely not aggressive, I've had people ask to pet him (and sometimes not ask) while he is doing this and he just maintains his position. It allows me to maintain my personal space. The issue I have is that I get very paranoid when I am around strangers in public. I constantly believe that someone has the intention of harming me, kidnapping me, or stealing from me. I also have a difficult time interpreting the expressions on people's faces and/or their body language. Often, this means I cannot figure out if they are friendly or have ill-intentions. Because of my paranoia, I tend to assume they have ill-intentions or are trying to pick on me. So...Sheriff "Covering Me" allows me to better gauge the person from a comfortable distance so that I can interact with them.
Before Sheriff was trained and when I was still often psychotic, I was extremely paranoid of police officers, even though I have never done anything to break the law...not even a traffic ticket. However, I was once psychotic and my parents called the police because I walked out of their house with the intention to walk about 5 miles back to my apartment (my mom wouldn't let me drive and had taken my keys away) and it was night time. Therefore, they called the police. I was highly paranoid and anxious and had no clue what the officer intended to do when he finally arrived. I was somewhat cooperative until he began mentioning that he thought I should go to the hospital and get checked out. At that point I panicked and started trying to get away. Luckily, the officer knew that I was not in a good place mentally and somehow regained my trust quickly enough that he was able to trick me into allowing him to pat me down. He then, quickly but gently, got my arms behind my back and before I was aware...I was handcuffed. The situation could have been A LOT worse.
If I had use of my service dog back then, I wouldn't have had such an issue. I have been confronted by officers since then (not for the same things but they still make me paranoid) but Sheriff's presence causes me to remain calm and cooperate with the officer. This works in any other confrontational situation...maybe not confrontational...any situation in which I feel is threatening (regardless of the reality of the situation). Sheriff allows me to maintain my personal space and I am given time to assess the situation and learn what the person wants or needs from me...and I am less likely to react from the paranoia. Again, Sheriff is not trained to attack but the way that he placed himself in between me and another person gives me the time I need to analyze the situation and act more appropriately instead of allowing panic or paranoia to rule my reactions.
He also does the "Cover Me" task in reverse by turning and sitting the opposite direction that I am facing when I am standing still. It makes me feel safer because I assume someone would be less likely to approach me when a dog appears to be "watching my back."
I don't know how legitimate these tasks are. They are trained and as Kirsten said, they address a disability involved in my ability to think. Also I saw a statement in which a DOJ spokesperson stated that they do generally regard anxiety as a disability...and this task partially addresses anxiety and also addresses my schizophrenia. Both of these affect my thinking and reasoning abilities. So yeah...not sure if this information and examples help but I just thought I would add them. Sorry if it was a bit off topic...today has been a day of rather disorganized thinking.