No idea what the history of that frame is.
The frame could have been a customer or shop return (for cause), and someone looked at it, thought it was "good enough", and put it back out.
Or, perhaps a return (or dead stock, or display return) that came back, got stuffed in a corner for a couple of years, then someone looked at it and sent it out.
Part of the answer might be what kind of box it came in. Even if well cared for, a 2 or 3 year old box won't look pristine. So, if the box looked new, it probably had been reboxed. There might be even marks or labels on the box indicating history... Security tape being opened and repackaged?
I do think the ad should have had a disclaimer. And, if it is a one of a kind, then it should come with photos of that bike. If it is one of several, then perhaps a general disclaimer indicating the condition of the parts.