Billy doesn't even tie up two defenders all the time; last year he was frequently stopped by one defender even with a run up. I assume it's because he runs straight at them, not at shoulders.All our carriers tie up 2 defenders as the ruck ball and Young's are so slow and predictable. It's been like this since last year. Curry can do exactly the same job and do it better and then there's actual 8a to pick as well.
Contrast that with Genge or LCD, who run at shoulders and bump people; you'll often see one defender go at them, fail, and then require two more defenders as support. Or they break through and make meters. I much prefer the smart carrying over the heavy carrying, and I think it's a better fit for the modern game