Travel funds definitely work, the social media coordinator confirmed it on Flyertalk. Any revenue (points earning) flight will count - cash/credit, gift cards, travel funds, or LUV vouchers.
My other half has the pass through June of next year (SWA extended all 2020 CP expirations) but I might book a cheap RT to take advantage of this. Might even book a trip for our nieces to visit during the fall promo period - leave our options open to bring the whole family to Hawaii or somewhere in February. If it doesn't pan out, so be it.
This is a great promotion for people who have the risk tolerance for travel right now. I don't know if I'll be able to pull it off, but I'm interested in trying.