Even if they did, there's nothing wrong with it if you are aware of it and agree to it when you place your order. Some people might be willing to prepay an order in its entirety, even if it take months to fill, if this moves them to the front of the queue. At that long a wait it essentially becomes a custom order and it's not unusual for companies making items on a custom basis to get a deposit, at minimum, or maybe prepayment in full. See your local custom furnituremaker for examples.
If you have to wait four or five months to get a chisel, they ought to offer free engraving.