Each segment sticks to it's own 60 day window, for now.
I just called MS to verify. They said they used to be able to use the "workaround" you described above for split stays, but that has been "temporarily suspended".
Here's hoping that none of these "temporary suspensions" become permanent. This one is especially aggravating, as we typically do 4 nights at BWV and 4 at BLT ... It's really an 8-night stay, but we don't get the ADR benefit of an 8-night stay? Makes no sense.