There seems to be a question of what “custom” really means. I'm not sure if I can clarify this, or just add to the fog, but I’ll try. Very few cars, for example, start out as custom cars: they start out as ‘54 Fords, or whatever. If a person buys one and chops it, repaints it, changes the engine and exhaust system, etc., then it becomes a custom car. Some people might go the other way and try to keep a ‘54 Ford as close to the way it came out of the factory as possible, and while that might require as much money as customizing it would, it's done for a different purpose and doesn’t result in a custom car.
I could do the same thing with a bow. I could buy a ‘59 Bear Kodiak, not a custom bow, and change the grip and limbtips and make it into a custom bow. I don't know why anybody would want to do that, as it would ruin the value of a classic, but they could if they wanted to. OTOH, you could buy an already made bow from any bowyer who happens to have one for sale, and if he just ships it to you without changing it to suit your preferences, then it's not a custom bow. If you call a bowyer and agree on the poundage, the grip, the length, the tiller, the wood, and the finish, then it's a custom bow, even though he uses the same forms he uses to make all of his bows. Some ILF bows made with metal risers in factories may cost more and shoot better than some custom bows made by some individual bowyers, but they aren't custom bows unless you have enough clout to get the factory to change things to suit your individual preferences.
Another definition of custom would be a bow that is unique because of the material it is constructed from or other factors that make it one of a kind. An example of this would be a yew self bow. Every piece of yew is different, so every bow is going to be different even if the bowyer constructs each one as close to the same way as he can. The same could be said of some more modern traditional bows, but the differences are not as obvious to me as self bows. For example, I wouldn't consider a wood bow constructed in a factory custom, even though no two pieces of wood are going to be exactly the same.
The original question is a valid question, as long as we understand what the question means.