Yep, you're right. The top of the stand isn't solid. When I adjusted my eyes, I realized that through the opening, you can see the corrugated siding and the piece of diamond deck plate leaning against the siding.
I still can't say whether or not the legs are in fact welded or brazed to the stand. If the owner says that they are, then I guess that they are. But we don't know whether the owner correctly understands what part of what's visible came from Atlas and what part didn't. I'm afraid that the only way you are going to find out what the true situation is, is to go and look at it. Given the situation (where you and the lathe are and the general availability of machine tools in your area) I think that I would make the drive. But I would also be prepared to tell the current owner that I only wanted the lathe itself, and not the stand.