As a quick follow-up -- kudos and hats off to the excellent people at Southwest customer service, who I spoke with today. They agreed the language was confusing, discussed it internally and with their partners, and told me that I could, in fact, rent a car every week at the same location without the need for an airline flight. They said the way it's stated online is, at least in part, incorrect.
A lot of us come to these boards to gripe. I'd like to break the mold a bit and pass along a "job well done" to Southwest customer service.