I don't know about "these days". I don't think there's ever been a suggestion that you get further up the list by being a member. When I asked the ACO about this the only thing mentioned was the 15 year "magic list". ACO membership just gets you cheaper tickets and entry to members' areas.
When I did my little survey a couple of years ago it was clear that allocations were made in date order according to when they were submitted, and that the letters were sent out in customer number order. But of course, things do change....