No, it appears to run in a batch mode at set intervals rather than in real time. To me (as an IT guy), it's more of a philosophical decision with both approaches having their pros and cons.
Waitlist requests are only filled if a match is made for the entire duration. If you waitlist 7 nights and 3 come available, there's no match. And the system will not hold those 3 nights in anticipation that the other 4 *might* eventually open up. If the system were run in real time, the odds of a match would decrease because the only time a match would occur is when a single cancellation matches an entire request.
With the batch process, there is a greater chance of multiple cancellations contributing to a match. In the example above of the 7 night trip, imagine one member cancels 3 nights at 5pm and a second member cancels the other 4 nights at 8pm. When the batch process runs at 10pm, ideally it finds all 7 nights and the match is made. Of course, this comes with the potential drawback that someone could log in and grab some or all of those dates before the batch is run.
If you brainstorm the entire process, there are drawbacks either way. I don't see any clear reasons to say that one approach is better than the other. To answer OP's question, I've had success with the waitlist almost every time we used it. Granted, we steer clear of the absolute toughest resorts and room categories--you're not going to have much success waitlisting BCV studios or AKV Value. Also, getting 2 nights off the waitlist will always be much easier than 7+.
I also wonder if we don't over-estimate the number of people who are stalking the website, grabbing rooms as soon as they are released. There is no-doubt a lot of attention paid at the 7 month window when people are jockeying for different resorts. But I'm not sure there are many people logging in 5x per day, trying to find a room for some random dates that are 4-5 months away.
In OPs case, I think there's a very high probability that the match would have been made last night when the batch process ran. He just happened to manually grab the rooms before that occurred.