I would highly argue the “recent frequent travel” theory. I have been traveling a ton lately and have still ended up at A30 with people who have traveled less recently. My personal theory is the same metric for the actual check on time. Meaning someone who gets to check in more than 24 hours before the second segment of their flight than the person who is only on that flight. I would assume the same principle applies at the 36 hour mark for those connecting versus that being their first or only flight.