It could be an accident but this is what it says on their ad page.
Edit: Maybe they just meant you can look at what's in the store online... in which case that's some confusing and terrible wording but technically valid I guess.
It's supposed to work online, it's only on preowned games but the above link was for all games under $4.99.
I can't post an image because I have less than 3 posts (wow I'm a veteran lurker, I've been using this site for years) but if you click the ad on the website that says 4 for $10 and...