No, what he said was you shouldn't judge someone as harshly as was being suggested by one piece of non-verbal communication. And he's right. You'd be an absolutely terrible interviewer if you held everybody to such an arbitrary standard.
If you had been my interviewer more than three years ago when I first applied for a job at a graphic design studio, I most likely would not have been hired because back then I had very little self-confidence. I hadn't had a serious job before and the company I went to was quite well-known and had high standards. Despite all that, eventually I ended up working on some really nice projects with them. And by working there I learned quite a lot about clients, projects, deadlines, coworkers, talking to people on the phone, planning, designing and programming, and probably loads more that I can't come up with right now. Looking back, it was more important an event to me than anything else. I've since quit working there to be a freelancer.
And to think I could have been rejected based on something so simple as a handshake. I must have been lucky that the owners of the company weren't stupid enough to believe that if you're not good at non-verbal communication you must OBVIOUSLY be a terrible employee.
You go on as if I said its the make or break deal. Even when I said it wasn't .... Their are tons of factors that go into that decision, your field, or your work, who else were they looking at, where you live. If your work was amazing or at least better than all the other candidates, then their was no reason to give undeserved value to your subtle body language. This weights heavily on when the employer has a lot of options who are close in skill, he has to start to take into account little things.
No one is saying shy people don't hired, or weak body language is the key to a job. it's just what you can work on for an interview, chances are if you have an interview you already have a resume and work history, what else can you improve for an interview that's coming up in a week? I can't account for all the things that go against my experience and what I learned but I never said it was black and white in the first place.
However to assume that people don't judge people by those factors is ignorant, yes some (whether it's a majority or a minority) people do judge harshly, so why even take the chance? No one is going to turn you down because you had a good handshake, you knew how to dress for the job, you were polite, you had good posture or because you were out going.