Well, as I said earlier, Dean is indeed invaluable. I called back MS this morning and quickly got to an exchange advisor. I explained to him the discrepancy between the
Sunday check in date listed on the DVC/RCI website for the resort I wanted vs. the available
Saturday check inventory Dean had found.
The CM I spoke said he was intrigued by the differences in days and put me on hold while he "
looked into this with some associates."
Well, voila -- he came back a few minutes later and said yes, there indeed was the 2BR space I was looking for at my desired resort for several of the weeks I had listed, all with Saturday check in dates. He also admitted that neither he (nor any other advisor) would have caught this if I hadn't mentioned it. He attributed the discrepancy to the fact the program is only three weeks old (i.e. they are still working the bugs out).
I ended up being able to confirm and book my first choice week

Not bad - a great exchange reserved only five and a half months out!!!
So again, a
BIG thanks to Dean and a moral to anyone else reading this who has or is thinking about putting in an exchange request: ask MS to search not just for dates using the designated day of week listed on the DVC/RCI website but also nearby dates NOT listed. You may end up with same pleasant outcome I just had!