Another "Is this still available?" Response

I just posted a seven year old, 17 foot RV trailer for sale on facebook marketplace. Ten minutes later I rv'd my first so-called response: "Is this still available?. Well, duh, I just posted it minutes ago! I heard somewhere awhile back that responses like that are not genuine, although I don't know what the problem or scam could possibly be. Anyone else know about this kind of stuff when trying to sell something? Thank you.

P.S. Just got a second response, the same wording from someone else.