I read the standard and it still dose not say that the tail should be less fuller than a leghorns tails. I think it would say it if it did. and looking at that leghorns tail you posted is not as full as the lehorns I have seen.
Yeah i know the leghorns wasn't as well spread as it should be because all the pics I could find they had pinched tails, but also on the standard it doesn't say well spread for the Sumatras, but it does on the leghorns, so I interpret it to mean that they should not be like the leghorns, or it would say well spread in the Sumatras, funny though how I found more pics of pinched tails in the leghorn than I do in the Sumatras, I like the tail when they are fanned a little but not spread out, unless they are excited, because most chickens do get all stiffened up and their tails get stiff as well, but just hangin out relaxed, I like them like 4-H girls, she said she was relaxed.
When I breed my Sumatras, I can take any of them and cross them so two heavy's together, two light weights, a light with a heavy and I get all three types no matter what I cross, I think most breeds do that, that's why people have to cull, but it is all what you decide to cull for. When we use to breed wyandotte bantams, they seemed to be one of the worst for ratio of chicks to show chicks, you might get one nice one in every 50 chicks, where my odds are so much better in Sumatras they are much more consistent, but don't get me started on the Araucana, people who want to show those... they get major credit in my book, they are the most difficult breed of chicken with lethal genes, and hatching, and you can breed two tufted rumpless together and only get one tuft, no tufts, tails.. they have to really Love the breed, they are very dedicated, oop, now I am rambling, guess I am to passionate about chicken.. funny get out at my car at a grocery store here and I hear, mom there's the chicken lady LOL yep I am pretty lucky I get to raise chickens!