It's actually pretty clear.
Animals whose sole function is to provide emotional support, comfort, therapy, companionship, therapeutic benefits, or to promote emotional well-being are not service animals."
It doesn't matter whether the dog is trained to provide that comfort or not, it still isn't a service dog.
When we get into "natural behaviors" let's be honest. Is a judge going to sit there and agree with someone claiming their dog is a service dog because it isn't naturally affectionate and they've trained it to act that way? Of course not. It's absurd.
I guess that if you've never trained a dog to do a formal retrieve you could get confused about retrieving being a natural behavior. Dogs aren't born knowing to go and get the one exact item you indicate, at the exact time you indicate, and to bring it and put it in your hand without dilly dallying along the way, mouthing or dropping delicate objects or playing keep away. There is a difference between a dog playing fetch, and a dog retrieving on command just as there is a difference between a dog being guided around by a leash and one heeling properly. A dog playing fetch (a natural or near natural behavior for many dogs) will not run immediately over to pick up a dime and bring it to you just because you asked. He won't also do it for keys, soda cans, telephones, socks, credit cards, and heavy book bags. The dime has no intrinsic value to the dog. He does it because he was taught to, not because he's hoping for a fun game.
Some dogs have certain drives that makes them easier than others to train, but no dog is born a full blown retriever. "Mouthy" dogs and thieves are easy to train as retrievers. I think I made some comment to that effect to Roxie earlier about her dog not having any natural drive to retrieve. Look at Luna's video and tell me you've ever seen a dog do that with no training. If I really needed a dog to retrieve items, would I, in all honesty, settle for a dog who likes to play fetch and might occasionally accidentally happen to bring me what I wanted when I needed it? Or am I going to want the dog I can count on to shove her face in icy water to get the keys I just dropped that we need to get back into the house or we're both going to die of exposure?
This is the whole problem with task shopping.
1. I want to be able to take Fido everywhere, but how do I justify it?
2. Look, retrieving is a task, and I can play ball with Fido.
Now compare that with:
1. I need to be able to pick up things I can't reach after I drop them. My ability to survive and to live independently depend on it.
2. A specially trained service dog would be able to do this for me.
The whole loophole thing is annoying and I blame task lists for perpetuating it.