The tail needs to be long enough to touch the hock joint. It should be "set on" so that it's down when the dog is standing. It's perfectly OK for the tail to be raised to the level of the back when the dog moves (or is excited), but it should be set on such that it never goes higher, or curls over the back.
I think it looks natural and right for a dog to move with the tail level with the back, or a little lower - a "dead tail" that's held down, even when the dog moves, makes me think that the dog is timid or unhappy. (Or worse, that the tail was "fixed".)
I've never seen that dog in person, and I didn't watch the Group on TV, so I can't comment on his tail.