Not necessarily, at least on the first point. Someone could be getting coached.
A few years ago, a coworker of mine hired a contractor onto his team and was convinced the person who actually showed up was not the person who he interviewed (over the phone). He also thought the guy who did show up was getting a lot of help day-to-day from somewhere. The guy was a contractor, so it wasn't a huge problem because we could drop him quickly, but I would have never expected someone would do anything like that. However, it kind of makes sense as a scam: be a decent developer, get a stable of unhirable incompetents, and rotate them through companies while taking a cut of their salary.