If the Swans match, every pick they have between 1 and 72 goes off the board to move them up to pick 1, effectivel removing 4 picks in front of our picks 59 and 60, which become picks 55 and 56. If they didn't match, we'd still get one of the two best players in the draft IMO.
So there is an advantage to doing it, but Weitering helps our list more than Mills, at least in theory. Melbourne will probably have a crack at Mills and Hopper, anyway, which should shuffle at least 2 live picks out of our way, if not three.
The further our 4th round picks move up the numerical order, the more they're worth against a bid on SOS.