I posted probably fifty ads there a few years ago, and I can't remember ever getting a single inquiry or bid- even for a few low dollar DVC contracts.
I've always thought it was just a lead generation site for another timeshare related business. If you try to follow the links to the privacy policy- it takes you to a dead link.
I'm probably just paranoid, but the site never seemed to get enough traffic to make google ads profitable. Maybe they get enough upgrades to make it profitable.