I wouldn't expect a Joe random robber a) to carry a knife usable for throwing; b) to know how to throw that knife. Most knives are as useful as rocks, when thrown.
Although in a real situation you might not want to test anything from this thread, because you could be very unlucky.
He probably should have said "less useful than rocks", because knives not specifically balanced for throwing would probably fly less accurately than most rocks.
I used to own a set of throwing knives. They're not exactly point and click and remember, thieving is an opportunity thing. They're likely to just let you run and steal an old lady's purse instead.
I agree, but I'd rather not turn my back on any antagonist with a knife. As another commenter has said, a 95% chance of getting stabbed are rather crappy odds.
Neither would I, but there's a lot of sick fucks out there and there's no telling what they'll do if they have you in a submissive spot. I particularly don't want them knowing where I live. Plenty of people have gotten killed because they got robbed and they didn't have enough money to satiate the thief.