Kai is spot-on. And I might as well chime in with a few details, since YJ is indeed just a man who does everything Moollon.
YJ does certain things in batches: pickup winding, neck and body shaping, application of lacquer usually in groups of three bodies per color, and it's not uncommon for him to take a few hours to work through a box of his tuning machines, selecting matching pieces and assembling them in advance for a month's future bass assemblies. Each respective final assembly is done one at a time, with some "parallel setups" of maybe four guitars and basses while each responds to full string tension on his work benches over the course of a few days.
Most lengthy wait times (such as the present "11 -12 months") discussed these days are the best estimates we can pass on right now. Some will be completed sooner, and due to circumstances sometimes unfortunately a little later.
But to be sure, some build times are extraordinarily long, irrespective of others being in line in front of one's order. We are fairly open to mention that Moollon is not a factory, and as YJ being human also makes him prone to the possibility of mistakes in a finish or finalization of an assembly (nitrocellulose lacquer will cry a goopy lump if you stare it down, you know).
Sure enough, if summer humidity at its worst or a fatal error in wet sanding is noted along the way, sometimes a single body or entire batch has to be redone, leading to unforeseen delays and much potential consternation on the other end of the email. And in other cases, a body simply comes out too heavy, so after discussion with the customer regarding foreseeable weight issues, a fresh batch from a lighter set of blanks may be in order. But honestly, we are not above being daft at times as well, and miscommunication between him and myself regarding a customer's request has led to us not getting the specs of an order exact right from the start, upon occasion. Note that it is not uncommon for a customer to decide on a finish after a dozen back-and-forths with us via email, and sudden changes immediately after finalization do throw curveballs into the mix.
All in all, if the current demand (we're not fond of the word "hype") eventually goes down, then so will the basic time estimate for the average build, but lengthy waits on top of that can (and will) unfortunately happen from time to time. In the meantime, we'll do our darnedest to keep things as close to as originally estimated.