Okay, I just spoke with Ms. McLane. I asked her specific questions about the prematch process and their typical acceptance patterns throughout the cycle. While this information is, due to the nature of the process, not extremely illuminating, it is more authoritative than our speculation. And there are a few pearls of wisdom here that might prove interesting to those of us still waiting for a decision.
She confirmed that the bulk of their prematch offers went out on the 15th. However, she said the Committee is planning to have several additional, smaller waves between now and mid December. Crucially, and I made sure to clarify this point, each time offers go out, the entire pool of applicants will be reviewed. This means that the later prematches are by no means reserved for candidates who recently interviewed; all interviewed applicants regardless of interview date are thus still very much in the running to prematch between now and around mid December when she confirmed that they will most likely cease extending prematch offers.
Ms. McLane also verified that very few people will receive new offers via the match. When I asked her if she could speculate as to what proportion of the class would be accepted off of the waitlist, she compared it to Vegas (and told me if she would make a lot of money there if she could answer that question). Finally, she stated that Southwestern typically makes somewhere between 350-380 offers in sum to fill their class of 230 students.
That's all I got. I honestly did not expect the office to be so tremendously helpful and receptive to questions; I've done my best to share what I learned with everyone else who is still waiting. I hope this helps. Best of luck to everyone and again congrats to those who've already gotten offers.