I don't think he's just full of talk on this one. He described a Stand on his own, without prompting. That's a hell of a thing to just make up — especially if you're not aware you're talking to another Stand user when you're doing it.

[Don't shake that at him. He tips it down with the flat of his fingers, lowering the point by a few inches.]

I'm willing to suspend disbelief. Better to err on the side of caution.