FluffyBunny, I had the same reaction to the ball-shaped comment that you did, and realized that they seem to be talking more about wild Cottontail rabbits than our domestic breeds. It makes sense in the wild, and if you look at lawn bunnies and others in natural habitats, their tails do seem small and round.
Our domestic pets are usually the result of years of breeding, even though we may not get them from breeders directly. Part of that activity is shaping the physique of different breeds, and I’ve noticed that some indoor rabbits have much longer tails that may be more flexible and expressive. My Spockie had a really long tail, for example. He was a Mini Rex. So the purpose and function of a tail will be different for a house rabbit. Ours tend to wave them like hands, especially when they are running away from doing a bit of mischief. Like a fuzzy wink. 
I’m sure that the existence of bone and muscle around it makes that intentional wiggling possible.