I agree with golfingdad, I think most every player is congratulated by their caddy first. Apparently he is a really good friend with AS, so to see a friend be happy for his mate? I don't see anything wrong with it. You re-watch it, and Adam walks up to him and hugs him again later, they seem pretty close to me.
I think people are a bit oversensitive about what he does because of the screw ups he made in the past. I agree, man that was terrible. He would freely acknowledge that they were screw ups too. Now I think people are willing to pin too much on him now. And the fact he's not from the USA, I think the media and fans would have forgiven him a bit easier if he was.
Whatever you think, he has to be one of the best caddies around. No, he didn't win the tournaments, he carried the bag. But as far as carrying the bag goes, he's got it.
You watch him helping read the last putt, tells him what he thinks, leaves him to it, and AS made it...