Just to follow up with my experience with Southwest.
I designated Southwest on 8/14, purchased $50 Southwest Gift Card on 8/19, and then subsequent $50 gift cards - all on different days to total $200. These charges stayed at pending for a week or two, then disappeared. Then the charges popped up again as regular charges a week ago. Just today, I got reimbursed for them.
So, Southwest definitely works - it just takes a few weeks to go through the whole process.