Question of best usage I guess. You want your backs in the backline, because they have the pace and ability to take most advantage of it. You want your tallest options generally leaping, since that's where height and explosiveness is more important. With all that said, you still want a skillful player throwing in, so they can take it at the back of the maul or similar.
Perhaps a flanker could be the better option, in, amusingly, the Ashley Johnson mould.