AFAIK these will be POD (Print On Demand) for a while, but FFG does not and cannot randomly guess how many to print and hope it all turns out OK. This is why YOU are the most important piece of this process. IIRC when the existence of these was made public the pre-order window was still open, so the way it's supposed to work is bottom-up demand generation.
People who play Armada bug their stores and give them an idea of how many they will need, stores bug their suppliers to make sure they get an order in the pre-order window and then suppliers/distributors tell FFG how many they will need to cover store demand and i assume FFG will typically print exactly that many and a few overs just in case. This explains why there is a gap between pre-order window and delivery and why if you miss the window you likely will not get one as none was printed for you!
From the outside looking in it seems "stupid" because somewhere in this chain where you can't see, something broke down and it's frustratingly out of your control, but when it works as intended it works well for everyone.
Sometimes people assume (incorrectly) their store will order these automatically
Sometimes stores forget to put in their orders and miss the window OR simply underestimate the demand!
Sometimes distributors don't think to order a couple extra to cover those stores (can't blame them, cause if no-one wants them they get to eat the cost)
so their numbers aren't counted towards the total and Bobs your uncle.