The biggest issue with pre-orders at KC is that they seem to do the least good job of estimating how many they'll receive, so there have been shortfalls, as you say. I have been buying from them since the 1990s and have never had a problem, and they have competitive prices and are very good about returns.
Yep, I've had some preorders with them that they couldn't fulfill, oversold more than they received. On the other hand, they required no deposit, and they don't charge your card until it ships, and they don't complain if you cancel the order because you found it available somewhere else. When I preorder a knife with KC, I understand I may be paying a bit more than if I wait and see if CS or KW gets the knife in, but if it is a knife I really want to be sure I don't miss out on, I'm willing to pay a few dollars more.