I would "assume" they are primarily are all made once they receive an order.
I would imagine they do this since they provide their customers with such flexibility in regards to what they can order. Frankly at that price I think I should have some flexibility. Besides I have no problem waiting 2 months for a pair of St. Crispins.
Leather Soul told me when I ordered my first pair earlier in the year that they make anywhere from 1200 to 1400 pairs a year. Who knows if this is an up-to-date estimate or not.